Chemo is a walking toxic waste vat with minimal intelligence. The only reason that he is sometimes difficult to defeat is because he is radioactive and can spew radioactive waste from his mouth at his enemies.

Seeking to conquer disease, famine and all the ills of mankind, Professor Ramsey Norton experimented endlessly with various chemical combinations, disposing of the results of his failed experiments by tossing them into a large man shaped plastic mold Norton called Chemo. Norton felt the presence of a humanoid chemical filled form would remind him of his failures and thus urge him to swifter success.

While experimenting with the concept of unchecked growth for fruits and vegetables as a cure for famine, Norton poured the results of his failed attempts into Chemo, filling the plastic figure at last. The exhausted professor fell asleep at his desk after deciding he would have to empty Chemo the following morning.

An unholy gurgling noise awakened the slumbering scientist, and he turned to find Chemo growing larger behind him, apparently taking on a life of its own. Before Norton could make a move to reverse the process, Chemo spit out a stream of volatile chemicals that incapacitated Norton and ultimately killed him.

Now possessed of some primitive malevolent intelligence, Chemo began a rampage of destruction that was only halted by the timely intervention of the Metal Men. Though seemingly destroyed by the Metal Men, Chemo has returned to life time and again to continue his campaign of destruction.