Includes:
- Body Parts (chewed, broken, missing) - Cancer - Cleaning Tips - Dyeing -
- Head Removal - Highligher MarksMold (brown, smooze/pin dot, pony pimples) -
- ​Plasticiser Breakdown - Regrind
- Rust (cleaning, sea pony weights)-
- ​
So Soft Ponies (cleaning, de-flocking, re-flocking) - Stain Removal (cleaning, sunfading, creams) -











 - Body - Hair - Symbols - AccessoriesMisc - Materials - 
Whether it be the family dog, or the child herself was the culprit, chewed body parts is extremely common in ponies.  This used to be a life ender for the pony, but now thanks to Sculpey, Apoxy Sculpt, and similar products, just about any of these defects can be corrected.  How well this turns out depends on how good you are at sculpting and mixing paint colors.  Practice makes perfect, and hey, what you do can't look worse than those missing ears, right?
Courtesy Salamandra.
Courtesy MustBeJewel.
No one knows exactly what causes pony cancer or even what it is, but the theory that it is caused by a deterioration of vinyl from age is the most popular. There is also some debate over whether or not it can spread to uninfected ponies.

There is no known cure, methods for preventing its spread range from rubbing it with acetone, bleach, and boiling infected ponies in OxiClean. There is a lot of debate about this as well as some collectors believe that moisture causes the cancer so boiling a pony will make it spread. However, the boiling method is the most popular and the majority of collectors swear by it.

The only agreed upon method seems to be simply to quarantine infected ponies by storing them in plastic bags away from other ponies. Many collectors also put moisture absorbers in the bags, such as silicone packs.
There have been reports of the cancer being lightened by sun-fading, rubbing the spots with acetone, and using Remove-Zit on yellow and white ponies.

Another method that is largely untested is to paint over the cancer, to simply hide it. This won't prevent its spread, but can potentially make the pony look better.
Photos courtesy nina85.
Luckily, the general cleaning of ponies is quite simple.  Dawn Dish Detergent will remove dust and a lot of surface dirt.  Sometimes it also seems to brighten the pony's color.  Mr. Clean Magic Erasers will remove more stubborn surface dirt and an OxiClean bath will get rid of more deeply embedded dirt and often brightens the pony's color.  Use pipe cleaners or bottle brushes to scrub the insides of the pony.  Every collector has his or her own favorite method and tools for general cleaning.  You'll quickly develop your own as well!  Yum-Yum at the MLP Arena has a cute cleaning video available here:  My Little Pony - basic wash and style tutorial.

To get to gunk inside your pony's body, you'll need something small and preferably flexible.  Children's toothbrushes, bottle brushes, aquarium filter brushes, and long handled q-tips can all be used to scrub hard to reach areas like toes and ears.
Dyeing ponies doesn't seem to have much usefulness for restoration and pretty much falls into the realm of the customizers.  I do have high hopes that someone will eventually find a way to fix regrind and hide stains using dye, so I'm including a tutorial about it.  The dye doesn't affect eye paint or symbols, but it will dye the pony's hair so you'll have to remove the hair while dyeing and then replace it, or do a complete re-hair once you're finished.  Keep in mind that the pony's original body color will affect the end result of the dye job. You probably can't turn a dark purple pony yellow, for example.
Photos courtesy Creampuf.  She also includes a very detailed dyeing tutorial if you have more questions!
Rit Dye is the most popular product for any sort of dye project involving ponies. It comes in liquid, crystal, and powder forms. You’ll have to decide for yourself which version you’re the most comfortable working with. It will stain surfaces and containers so be sure to cover counter tops and such with newspaper and use bowls and containers that will not come into contact with food. 

Heat the water to boiling, remove from heat, and mix in your dye. You can make the pony darker and/or brighter by letting it soak longer, or by adding more dye to the water. You can always put the pony back in the mixture or add more dye, so ere on the safe side and use less dye at first.

Continuously stir the water as your pony is soaking to keep the dye mixed evenly in the water. You can also hold the pony down in the water with tongs to help it absorb the dye evenly. Different collectors have different opinions on whether or not to remove the pony’s head.

After the pony has been in the dye for a few minutes, check for areas where the color is not changing due to the presence of excess glue. Sand off the excess glue, or remove it using acetone (this can also be done before you start the dyeing process, if the glue is visible), then continue with your dye job. 

Once your pony has reached your desired color, wash its body to remove any excess dye. If you also dyed its hair, you’ll likely have to wash it several times to get out all the extra dye. You might also want to give the pony an OxiClean bath.


                                                                                 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Customizers who dyed ponies several years ago are starting to see some fading and discoloration in these ponies.  This makes the usefulness of dying for restoration purposes even more uncertain.  See:  ​​​Why I don't Dye  Also use caution when storing dyed ponies as the dye can stain other ponies if they are touching.  Courtesy: BabyStargleamer

 ​​                                                                                . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Shadowlark at the MLP Arena donated photos of a badly faded SeaShell that she restored ​using dye.  She looks great!​​
You'll need to remove your ponies' heads to clean inside them, while boiling them, and for projects like re-hairing.

​​Lots of regular pony heads can be removed by gently tugging and squeezing at them.  Use a thin blunt object to pry off any sections that are still glued to the body.  X-Acto knives are very popular for this and the blades can be reversed to help avoid accidentally cutting into the pony's neck or body.  Pictured to the right, Sweetlittlejenny recommends a scrapbooking Scoop Tool for a safer version of this.

For tougher heads, dip dental floss, sewing cotton, or thread in nail polish remover or acetone, and use it to saw at the neck seam.

If you want, you can glue the heads back on using a craft glue such as Aleene's Tacky Glue or model glue, but you probably won't need to.  Luckily, ponies usually have small indentations on their heads and bodies so you can see how they're supposed to line up.
Ponies are made of vinyl, which is porous and prone to growing mold.  There are two types of mold most common in ponies, what I'm going to refer to as "brown mold" and "smooze", also known as "pin dot mold".  There is also a type of mold  that has recently been identified which I will refer to as "pony pimples".  Any type of mold CAN and WILL spread between ponies if left untreated.

Looking for some great info on how to prevent mold?:  Tutorial: Mold Removal and Prevention (For those in humid climates)​​ & That Funky Fungus
Brown Mold
The only way to tell the difference between brown mold and pony cancer is that this type of mold usually has a dark dot in its center. There is no known cure for this type of mold, but it is treatable using the same methods as pony cancer.  Update:  It seems that most collectors now believe that Brown Mold and Pony Cancer are the same thing, both caused by bacteria.  This would mean that brown mold is not mold at all and won't spread between ponies.  See:  Brown Mold . . . Can I Stop It?

Treatments usually involve one or both of the following, bleach treatments, and/or boiling/soaking infected ponies in OxiClean. Molds can't live without moisture, so be certain to dry the pony completely if you choose a method that involves water. Many collectors choose to quarantine infected ponies by storing them in plastic bags away from other ​ponies. Photo courtesy Raemarie.​​
Smooze/Pin Dot Mold
Here's a lovely tutorial courtesy Rhys:  Pindot Removal.

"Its rather simple. Things you need:
  • Bathroom/kitchen sink
  • REALLY hot water
  • smoozed pony
  • liquid antibacterial soap in a pump bottle for easy access
  • fingernails (or a small steel brush would do I suppose for the fingernailless among us)
  • patience
Run the water really hot, until it steams. Be careful to keep your fingers away from the stream! Now, after waiting for the water to get hot we take the pony and hold one affected area under the stream. For smooze removal, its best to tackle one area at a time.

You may have to hold the area under the stream for a minute or two. What we are doing is using the heat to open up the pores in the plastic. It doesn't hurt the pony, nor is it noticable. It just allows us the ability to remove the smooze.

Once you think its been long enough, add a dallop of anti-bacterial liquid soap directly to the smoozed area.
Now, lather the soap, rubbing it into the affected area. Once that's done, use your fingernail (or steel brush, you poor, poor fingernailless friends) to scrape back and forth across the smooze. Like you're trying to scrape a sticker off a packaging. Really scrub.
Rinse off the soap and check the area. This is where patience comes in. Some of the dots should be gone, but more than likely, you're gonna have to retreat. Hold her back under the water again, after a minute, lather, scrub, rinse, repeat if necessary.

The key is patience, patience, patience.​​
Ears - easiest to clean, Feet - next easiest, Wings - harder, but not difficult, Necks/bodies - woah, takes a TON of time, but do-able most of the time.  So grab your smoozed ponies, and get to cleaning!"
Pony Pimples
Raised dots and bumps on a pony's head or body that contain fluid or white goo are likely a type of mold.The bumps themselves are usually white or brown, but can be other colors.  Squeeze or prick the bump with a needle and let anything inside drain out.  Once finished, disinfect the area with any product you prefer.  Information courtesy Raemarie.

Bumps on the pony's head or body that are not filled with any type of fluid may or may not be mold.  Theories on what causes these range from a reaction to heat to reactions to chemicals in the pony's environment.  It doesn't hurt to disinfect these, just to be safe.
Photos courtesy Raemarie and Sea_Breeze.
Plasticiser is a part of the ponies' bodies and when it starts to leach out of them you can tell because they start to feel sticky. With some of the smaller accessories, like Brandy the dog or Twinkles the cat, sometimes it causes their paint and faces to smudge off. This can happen both inside and outside the pony or accessory.  Once the plasticiser is completely gone, the pony's body will be hard and unbendable.  You can likely soften the pony temporarily by applying heat (with a blow dryer or by boiling, for example), but the body will harden again once the pony cools down.

There is currently no known cure for this and it is believed to potentially spread to other ponies. The most common treatment for its breakdown is to wash the ponies with Dawn dish soap, dry them (usually by patting, rubbing seems to smear their plastic around), and sprinkle them with baby powder. This will have to be repeated every few months. Most collectors choose to quarantine them from the rest of their collection, but it is debatable whether or not it makes the breakdown process speed up if the ponies are stored in plastic bags.

The article: That Funky Fungus mentions a bit about plasticiser.  Another great article provided by Black CurtainsA Survey of Plastics in Historical Collections by John Morgan, provides some very interesting information about plasticiser:

"As with cellulose acetate, plasticiser is lost by evaporation and leaching, and through loss of compatibility through changes to polymer and/or plasticiser. Additionally, changes in compatibility of the plasticiser may have been brought about by adsorption of liquids applied to the surface in the form of cleaners and polishes . . . 'Squeeky' toys and dolls moulded from PVC pastes were often found to have a 'tacky' surface due to exudation of plasticiser, and to have stiffened considerably."
Regrind is believed to occur in vinyl where Hasbro "recycled" old vinyl by melting it and mixing it with another color.  It starts to show up as the vinyl ages and the colors separate.  Unlike pony cancer or mold, regrind appears in large colorful blotches.  It won't spread to other ponies and currently there is no known cure.  The only option right now is to paint over it.  Attempts to dye it usually end up with a pony that is darker in color, but still has mismatched blotches.

There is more than one report, especially in flutter ponies, of regrind changing the pony to an entirely new, uniform, color.​​
Photo courtesy Avea2006.
Cleaning

​​Rust most often occurs inside ponies that have been exposed to water.  They have metal washers in their tails and seaponies have metal weights in their bodies, which is why this occurs.  OxiClean baths will often remove rust.  For stubborn cases, try CLR or Rit Rust Remover.  You can use pipe cleaners, bottle brushes, long q-tips, or similar items to really get in there and scrub.  I personally put a little bit of OxiClean directly into the ponies body, making certain some gets into all the little spaces.  I fill the body with hot water and let it bubble for awhile, then rinse.  This usually gets all the rust and gunk of of the tiny crevices that are super hard to reach.  Make sure to remove the weights and washers from their bodies and tails.  Removal and replacement of the tail washers is discussed in the
hair section of the site.
Magic Star was cleaned using OxiClean and bleach.
Photos courtesy Emery.
Cleaning

Dawn dish soap rubbed on with a soft tooth brush will remove most dirt and even dried stains from so soft ponies.  Wet the pony first then apply the soap.  GENTLY scrub with the toothbrush.  Pat as much water off them as you can with a towel or napkin.  When the pony is dry, gently brush the flocking with a dry soft toothbrush to re-fluff the flocking.  If you need a stronger cleaner, the spray on version of OxiClean can safely be used on so softs.  Many collectors also use spray on carpet cleaners.

​​For more heavily stained, or completely yellowed so softs, many collectors have had luck whitening them with a bleach bath.  Use bleach with caution as other collectors report bleach having made their ponies even more yellow.  The amount of bleach seems to be pretty arbitrary, but over all people seem to use a pretty weak bleach/water solution.  This is often used in conjunction with sun fading.  Be extremely careful as the bleach will fade the ponies hair, so don't let them soak for too long, and this cleaning method seems to be safest on white ponies.  Be certain to 
thoroughly rinse off any chemicals you use and it's best not to use hot water on so softs.
The method of de-flocking so soft ponies that involves the use of Acetone and Jasco seems to be the most popular. Wear rubber or latex gloves while doing this as this method uses multiple nasty chemicals. Also be sure to work in a well ventilated area and follow all directions provided on the product’s label. 

First, soften the glue that is holding on the flocking soaking the pony in an OxiClean bath of hot or boiling water. Scrub off as much of the flocking as possible using your fingers or a toothbrush. If you choose to use a brush, be careful not to scratch painted areas like eyes and symbols. Rinse the OxiClean off your pony once finished. 

Next, using cotton balls, rub the non-painted areas of the pony with Acetone. Do not let it touch any painted areas as it will take the paint off. Once various body parts are wet with the Acetone, you can GENTLY scrape off the flocking and glue with a sharp object. You can soak non-painted body parts directly in the Acetone to help them soften more quickly. Use Acetone and or a gentle sanding to remove any excess glue from the pony. Rinse the pony again, also washing it with Dawn dish detergent as needed. 

Wet the painted areas of the pony with Jasco. Remove the flock off the painted areas by scrubbing them with a cloth, cotton ball, or toothbrush. The Jasco miraculously doesn’t remove paint from the pony, but be careful not to scrub so hard that you scratch the paint.  Also, use your common sense, it will remove symbols and eyes if you aren't careful and gentle. Rinse the pony again, also washing it with Dawn dish detergent as needed.  
You’ll probably need to condition your pony’s hair once this is finished. 

Contact your city or county to find out how to properly dispose of your left over chemicals. You should never dump chemicals down the drain.

Here's a nice video tutorial courtesy the Retroblasting folks:  My Little Pony So-Soft Restoration: Part 1 - Deflocking​​

Cleaning​

​​Try Mr. Clean magic erasers and gentle cleansers like Dawn dish soap first for a good surface cleaning.  If you used them for general cleaning, and your pony still has marks, try rubbing a little harder.  Remember to be careful over any painted areas.  It's really amazing the marks magic erasers can get off of ponies.
These pen marks were removed with a magic eraser.  Photos courtesy BabyIceCrystal
Rub at tougher stains and marks with a q-tip and nail polish remover.  Nail polish remover with acetone tends to work best.  Be careful not to get any of the remover on the painted areas of the pony as it will take them off.
Sun-fading will fade many stains completely away, and is usually the next thing collectors try before harsher chemicals..  Cover everything but the affected area (especially hair, symbols, etc.) with aluminum foil or paper towel and leave the pony in direct sunlight for as long as needed.  This can be weeks or months and works best in areas that are particularly sunny.  While covering the pony with aluminum foil is quite popular (they call them pony-tatos like baked potato), this can have a yellowing effect on their bodies.  No such problems have been reported when using paper towel, napkins, and similar items.

Sun-fading also works well to lighten the bodies of ponies who have yellowed over time.  This technique is usually used on white ponies, but can also brighten colored ponies.  Use aluminum foil or painter's tape for delicate surfaces to cover all painted areas.  Be careful when using painter's tape on glitter symbols.  There have been reports of it removing the glitter.  As with marks, the amount of time varies that the pony will need to be left in the sun, but it usually takes quite awhile.

This photo, courtesy of Relcelestia, shows the difference sun-fading can make.  The body has been sunfaded and the head left alone to show the contrast.  The time this takes is certainly worth it!

SoSoftClaire at the MLP Trading Post has provided some great information about how sunfading works:

"A little about the science behind fading:  What causes fading? Photodegradation.

It is all about the chemical makeup of an object. The technical term for color fading is photodegradation. There are light absorbing color bodies called chromophores that are present in dyes. The color(s) we see are based upon these chemical bonds and the amount of light that is absorbed in a particular wavelength.
Creams

​​If everything else fails, products like Removzit and acne products containing 10% benzyl peroxide, such as Clearasil or Persa-gel, can remove many tougher stains.  Rub the affected area with your chosen product and let sit 15 - 30 minutes.  Rinse and continue to let the pony sit.  These will usually continue to lighten the area for awhile after the product has been removed.  Repeat as necessary.  Be extremely careful not to leave the product on for too long as it is possible to over-bleach the stain.  Be aware of the color of the pony that you are working on.  These are relatively harsh treatments can fade or yellow the bodies of certain colors of ponies.  It's always best to test in an inconspicuous area.  RemoveZit works best on white, yellow, pale pink, or flesh-colored ponies.  It leaves marks that look like regrind on many other body colors.  Benzyl peroxide works best with yellow and orange ponies.  Test it on white and pink ponies, do not use it on green, aqua, blue, purple, and deep magenta ponies.

Creams can sometimes whiten yellowed ponies when other methods don't work.​​
BlackCurtains has recently found evidence that  smooze is actually dirt ingrained in the ponies' pores.  If this is true and it's not mold, then it won't spread to other ponies.  See:  I've Replicated Pindot (lots of pics)
"1st off- I am using standard hdrogen peroxide 3% solution. (Scientific shorthand is H2O2)  It can be found very cheaply at pretty much any food or drug store. It is commonly used for disinfecting cuts, and is very safe, unlike many of the products we use for cleaning ponies.  Obviously do not drink it or get it in your eyes. Buts its fine for using bare handed. (I still rinse my hands off afterwards)
 
For prepping the bath- Use any clear glass or hard plastic container big enough to submerse your pony in. I use small clear square and round vases... what else are they good for? (LOL) Pour enough hydrogen peroxide into the container so your pony (or pony part) is fully submersed. Its easier and more effective to take off the pony's head, and remove her tail. Place the container in a south facing window (that doesnt have uv film on it). Cover the container with a clear lid or plastic wrap, to help prevent evaporation. H2o2 is very sunlight reactive (Actually uv rays are what do it)! So depending on where you live and your weather, this may take more or less time for you. Here in MN Its been too cold to put my containers outside, but properly covered and safe from curious pets/wildlife I think it should be even more effective done in full sun outside.

So far, I have had absolutely no damage to any paint or glitter symbols on any pony I have cleaned. If anything I think it can make light paint, such as blush, brighter and more obvious (see the glory pics). Hair texture and color has not appeared to be affected so far, even after soaks for as long as a week and a half. However, see the caveats re: glue!
 
Whitening yellowed/ivoried ponies: . . . this is a wonderful technique for helping restore ponies back to their original whiteness. I placed glory in the h2o2 bath for 2 days. I flipped her over once in the morning of the second day. After 2 fully sunny days, you can see the results! Shes a gorgeous bright white, her head and body are now the same color, and I had no damage to her glitter symbols. I took her out and rinsed her off, the morning of the 3rd day, then once fully dry, gave her a full shampoo and condition. She hasn't looked this good in years.
 
Caveats:
 
Twinkle eye paint: I did notice some reduction of the pearlized twinkle eye paint on my gingerbread. She had really bad cancer spots and regrind. I soaked her for about a week, after which, her color was much more even. However her eye paint, which was not heavy to begin with, did look reduced.
 
Hair glue: Hydrogen peroxide does seem to loosen mane glue! Again with the same gingerbread, I rinsed her off, then washed and conditioned her mane right after her week long soak. A small amount of her hair did pull out. I have not had that happened since I went to the rinse, dry, them wash procedure.
 
So soft flocking: Like many other cleaning procedures, Hydrogen peroxide seems to loosen flocking glue. I had some flocking loss on a terrible mangey SS surprise I tried whitening. So i do not recommend this treatement for so softs. (On the other hand... it may be a slightly safer way to handle de-flocks... if you're patient enough)."

                                                                           . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ​​

​​Please also note that Chartreuse colored hair will bleed onto the ponies' body when soaked in peroxide.

I've also noticed a tendency for certain colors of hair to fade when using this method.  Namely red and pink, which is to be expected since pink hair fades for absolutely everything.  For ponies with hair colored variations of red, traditional sunfading with the hair covered is probably your safest bet.

In this thread:  I hereby challenge the needfulness of "peroxide fading"​​, there are some concerns noted about this method including potential for damage to a pony's hair and symbols.  Other than what is listed above, I haven't found this method to have any negative side effects and this thread seems to be mostly conjecture.  I'm liking this method more and more but am watching to see if any issues show up after some time has passed.  So far the ponies that I peroxide faded more than a year ago still look great.  If any issues show up, I'll be sure to post it here.  You can see pictures of my peroxide results in the "My Collection" section of the site.  More photos are on their way!
De-flocking

De-flocking a so soft isn't exactly a restoration, but sometimes their flocking is just beyond hope.  For these so softs, de-flocking is often a second lease on life.  A brightly colored very pretty second life, it turns out.  They're actually quite colorful under all that yellowed flocking!
Re-Flocking

If you'd like to re-flock your deflocked so soft pony, here is a lovely tutorial by CherryCake on how to do so: So Soft-Ifying Applejack.  Flocking is available at various craft stores and online.  You can order it at restoredoll.com or at Hobby & Craft Flocking and Supplies.  So far, no craft flocking has been found that matches the texture of the original so soft flocking.  You can use the craft flocking to touch up rubs on your so soft ponies, but the texture will not match and the difference is visible.
Sun-Fading

Yellowed Bodies

See the section on sun-fading under "stain removal" to see an often practiced method for whitening yellowed pony bodies.

Templeflower has also reported good luck whitening ponies whose bodies have yellowed using a hydrogen peroxide/sun fading treatment.  She's provided a detailed tutorial below.

​​I think the photos of Daddy Apple Delight whitened using this method might end any doubts collectors may have about the times when this is necessary along with sunfading. Photos courtesy Himmie.

This most often occurs when a ponies legs are bent in a funny way that prevents it from standing correctly or have dents in their bodies. 

A great suggestion, courtesy ladyphoenix9, is to take off the ponies head and fill it with boiling water.  Let the pony sit until the water cools, then dry the pony out.  If this works properly, the water will reshape the pony's body.

Other methods involve boiling the pony, then stuffing paper into it to help it hold its shape while it cools.  Hathorcat recommends popping the pony in the freezer while it's still hot to help the shape set.

​​When the issue is with the legs, usually putting something between them (VHS tapes and some books are usually the right thickness), and letting the pony sit for a period of time will shape the legs back into place.
Photos courtesy Breyer600.
Home - Goals - Restoration - Body - Hair - Symbols - Accessories - Misc. - Materials & Directions - FarDreamer - Links -
Ultraviolet rays can break down the chemical bonds and thus fade the color(s) in an object - it is a bleaching effect. Some objects may be more prone to fading, such as dyed textiles and watercolors. Other objects may reflect the light more, which makes them less prone to fade.  (Taken from a Library of Congress website about Everyday Mysteries.)

Light + ponies (and other items that have pigment or dyes) = photodegradation."

​​​Sunfading Tutorial courtesy Relcelestia

​​ A cool sunfading experiment!​

Paint and sunfading tutorial! courtesy Tehrin.  More information about using paint:  Sunfading TAFs??? Next Question....

Please read ​​Who Shouldn't Be Sunfaded? and List of Ponies Safe/Unsafe to Sunfade?

Sea Pony Weights

To remove sea pony weights, first remove their head.  A lot of times the weights are loose and will fall right out.  Sometimes they have one weight inside, sometimes two.​​

Photos courtesy Whizzer19, who also has a very nice Sea Pony FAQ.​​
If the weights do not come out easily, use a tool like needle nose pliers, tweezers, or hemostats to pull them out.  At this point, your pony is probably going to need a really good internal cleaning.  If you'd like the pony to float correctly, a great tip from Whizzer19's site is to put a glass marble in her tail.  This will keep it from rusting again!

Photos courtesy Eldarwen.
Photos & tutorial courtesy Maycrestmom.  In this thread:  Deflocking Advice?, there's  alot of good info an additonal tips about de-flocking.
Also known as saddle sores, theories on the cause of these marks range from thousands of marauding, pink highlighter wielding, children set loose during the 80's, a type of regrind, a type of pony cancer (breakdown in the pvc), and contact with pink accessories such as saddles, bridles, and shoes.​​ If the marks on your particular pony are caused from pens, highlighters, or contact with accessories, then sunfading or other stain removal techniques should remove them.  
​Photo courtesy Jaybell.
For smooze that isn't ingrained too deeply into the pony's vinyl, sometimes rubbing it with acetone fades it. Mr. Clean Magic Erasers and/or boiling/soaking in OxiClean often removes it. For smooze that is embedded more deeply than this, you'll need to do some serious scraping.
For really hard headed ponies, apply heat by dipping them in hot water or blowing on the neck seam with a hair dryer. This helps soften both the vinyl and the glue. Be very gentle when pulling on the head, you don't want to rip any of the vinyl.
Yellow marks are most often caused by ​​bleeding from chartreuse hair.

​​Avoiding the use of chemicals on this color of hair and preventing wet hair from touching the pony's body will help prevent this from happening. It can usually be sun-faded away.  Photo courtesy elish2.

Hathorcat recommends a vinegar treatment to help set the color if you want to prevent bleeding due to environmental factors such as humidity.  Please note, this will help, but won't fix the problem entirely.​​  Place tissue paper or a kleenex between the hair and the pony's body during storage.