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.
Dr. 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.
Smogulan scientists have discovered a huge pool of high smogtane crude that could fuel a shuttle to Tromaville for all their residents. There's only one problem, it's located under the Crusaders home base-the toxic waste dump.
Humanoid insect Czar Zosta, Dr. Killemoff's boss, arrives with his huge, ugly, vain and always hungry daughter Princess Gerba of Smogula to Tromaville. She falls for Toxie and forces him to marry her or her dad will destroy Earth.