His real name was Ron Palillo, but he will always be known by Arnold Horshack from 'Welcome Back Kotter,' a show my sister and I never missed in the 1970's.

Palillo died today at his home in Palm Beach Gardens, Fla. He was 63.

Initial reports are that the actor had a heart attack and passed away in his sleep.

Horshack was one of the Sweathogs on the hit series, along with John Travolta as Vinny Barbarino, and Epstein/Robery Hegyes.  He died in February at the age of 60.

Source:  NBC News