Nerdy loser Melvin falls into a barrel of toxic waste left by an alien insectoid warlord Dr. Killemoff who wants to pollute and take over the Earth. However, Melvin mutates into a hideously deformed superhuman Toxie and fights him.
Killemoff's mad scientist Dr. Bender creates a chemical that makes people old and senile. Toxie and his mutant friends must stop people from eating junk food with it in it. Meanwhile, Bender gets accidentally merged with airhead Fender.