Believe It or Not, Joe’s Walking on Air is episode 3 of family guy season 06. It was originally aired on October 7, 2007.
After Joe overhears Bonnie’s phone conversation, in which she tells a friend that she is tired of being married to a handicapped person, Joe decides to get a leg transplant. Excited about his new ability to walk, Joe dives head first into extreme sports and begins to hang around more active friends. Meanwhile, Peter and the guys are upset at how Joe is acting and decide to teach him a lesson. In doing so, they re-cripple him and he is back to normal.