King of the Hill Season 5 Episode 19

While preparing for the big lawn mower races in Durndle, Hank experiences back trouble. When he goes to the doctor, he is told that he has a genetic disorder called Diminished Gluteal Syndrome (DGS), meaning that he has such a small rear end that it puts added stress on his spine. The doctor gives Hank a prosthetic butt to wear, but the shame of it is too much until Peggy gets him to go to a DGS support meeting.