Ron Palillo, best known for his role as Arnold Horshack on the 1970s TV sitcom "Welcome Back, Kotter," has died, the Palm Beach Post reports. He was 63. He died at 4:30 a.m. at his Palm Beach Gardens home, a friend, Stacy Sacco, told the paper . Palillo had been teaching at the G-Star Academy, a Florida charter school. He previously taught at his alma mater, the University of Connecticut, according to Corporate Artists , which employed him for speaking gigs.