But Palillo has moved on. He has officially retired his ultimate crowd-pleaser, the Horshack laugh -- a gag that has haunted him for years. "You know where that came from?" he says. "When I was 10 ...

While "Welcome Back, Kotter" was a ratings success and the show helped launch the film career of co-star John Travolta, Palillo struggled to expand beyond his role as Horshack.