Ron Palillo, who played Horshack on the 1970s sitcom WELCOME BACK, KOTTER is dead at 63, according to TMZ.Palillo's character was known for the way he caught Mr. Kotter's attention in class with his, "Oh! Oh! Oh! Mr. Kotter!" on the show that ran from 1975 to 1979.
After the show was canceled, Palillo appeared at as guest star on television shows throughout the 1980s and 1990s, such as CAGNEY & LACEY, and did voice work in cartoons.