Thursday Man was the villain of the two-part series finale The Ripping Friends.
Background
Thursday Man lived in the future, in the "World of Next Thursday", where everyone has enormous thumbs sticking out of their chests. He was once a fan of the Ripping Friends, and heard about their exploits by reading their comic books. One day, his thumb was severed due to an accident. The doctors save his thumb, but was unable to reattach the nail. Until he was told about the great surgeon, Dr. Slab Friend. He built a time machine wiener car and traveled to the past of "Next Tuesday", where he arrived at the medical center of RIPCOT (the Really Impressive Prototype City Of (Next) Tuesday). But he had to wait til Wednesday because Slab was on an assignment. As he waited in the surgical ward, people were disgusted at his disfigurement. When Slab returned, he was able to reattach the torn nail, but since he came from a race that haven't evolved chest thumb, he accidentally put it on the wrong side of the thumb. So he pledged for the day to get revenge on Slab and the other Ripping Friends for making him a freak.