Skumm Lord Captain Planet and the Planeteers : Season 1 Episode 4

Venomous Skumm introduces his new formula, rat rot, into the local water system. It transforms anyone who comes into contact with it into mutant rats. Skumm's goal is to turn the earth into a planet-wide vermon carrier. His plot can only be countered by the Planeteers and Captain Planet, but not before some of them accidentally get a dose as well.