Pony cancer or, as it is officially known in the toy collecting community, vinyl discoloration syndrome, is a permanent discoloration and deterioration of the vinyl used to make my little pony and all other lines of toys and actions figures of the 70's and 80's. It comes from any number of conditions: having water trapped in the inside of their bodies, being stored in high humidity and high heat areas, poor plastic setting at the factory, and it can spread from other ponies who already have it.

This type of mold is what I call "center dot mold". It's usually found on seaponies, but I've also seen in on BnG Ringlets and Sunbeam so it's not limited only to them. It's characteristics include a dark brownish dot in the middle with a lighter brown discoloration surrounding it. This type of mold spreads very easily and rapidly. However, to prevent spreading, simply dip the pony in a light bleach solution and let sit for 10-15 minutes. As an added caution, I always take nailpolish remover and rub it vigorously over the affected area. It does lighten up the center dot somewhat and also helps to prevent spreading.

This mold happens when interior mold (due to heavy play in the bathtub) is allowed to sit inside the pony for long periods of time. Eventually, the black mold inside the pony permanently discolors the outside of the pony. This can be solved by popping of the head of the pony and cleaning out the inside. This will help to significantly lighten the stains. It can also be caused (as in the case shown in the picture) from the iron weight in the bottom of adult seaponies tails. For whatever reason, Hasbro decided to use one of the most rust worthy metals they could find. Go figure. This type of mold can spread within a pony but doesn't jump from one pony to another. The best way to fix it is to clean the interior mold and once again, allow the pony to sit in a bleach solution for 10-15 minutes. Do not re-attach the head to the body for a least 3-4 days while the pony dries to prevent a new flare-up.

This is a phenomenon called "Regrind" (see the link at the bottom of the page) This type of discoloration DOES NOT spread. It's found mostly in ponies released near the end of the My Little Pony era. The earliest pony I've ever seen this in is TE Speedy. Hasbro was loosing money on MLP's and decided to cut costs by melting old plastic in with their new plastic. The problem with this is that the old plastics didn't hold the dyes as stronly or for a long as the newer dye. Over time the plastic lost some of it's dye and became a different color than the surrounding plastic resulting in blotchy patches.

This type of mold is commonly referred to as "pin dot" mold. It only affects the outside of a pony and is usually due to poor storage condition. It does spreads from one pony to another. In order to stop the spreading, simply soak in a light bleach solution from 10-15 minutes (no need to pop the head of the pony to do this). After the soaking, prop your pony up on her rump so the water can drain out of her tail and just let her dry for a few days. For added precaution, run over the affected area with nail polish remover. If you want to get rid of the mold entirely, I have heard of some intrepid people who have taken a pin and removed each dot of mold one at a time.

The following method is credited to Sugarberry. Thanks so much!

• MLPCB Salon: detailed descriptions on how to remove some types of pony cancer