Ron Palillo

WEST PALM BEACH, Fla. — Ron Palillo, the actor best known as the nerdy high school student Arnold Horshack on the 1970s sitcom “Welcome Back, Kotter,” died Tuesday in Palm Beach Gardens, Fla. He was 63.

Palillo suffered an apparent heart attack at his home, said Karen Poindexter, a close friend.

Palillo was inextricably linked with the character he played from 1975 to 1979 on “Kotter,” the hit ABC sitcom, in which title character Gabe Kotter returns to his Brooklyn alma mater to teach a group of loveable wiseguys known as the Sweathogs. Horshack was the nasally teen who yelped, “Oooh, ooh,” and shot his hand skyward whenever Kotter posed a question.