Jack Rabbit is the main villain of the episodes The Wrong Stuff and Freaky Spy-Day. He was a former T.U.F.F. agent, working as Kitty Katswell's partner before Dudley came along. During The Wrong Stuff, she met up with him and he tried to convince her to leave T.U.F.F. for his new agency called S.T.U.F.F. (Super Turbo Undercover Fighting Force). It turned out his agency was actually a ruse for his plans to kidnap Kitty, drain her knowledge of T.U.F.F.'s secrets from her brain, and sell them to Verminious Snaptrap in exchange for money. He nearly succeeded, until he was foiled by Dudley and Keswick and he was sent to jail.
In the Season 2 episode Freaky Spy-Day, he said that he had a change of heart and asked Kitty to meet up with him. But it turns out he was tricking her again and was nearly able to steal a top secret card containing T.U.F.F.'s secrets from Dudley (who was in Kitty's body), before he was foiled.