Ron Palillo, best known for his portrayal of Horshack on 'Welcome Back, Kotter' has died.

He was 63.

TMZ reports the actor died early this morning of a heart attack.

He was reportedly a heavy smoker, but otherwise seemed in good health.

Robert Hegyes, the Kotter co-star who played Epstein, died earlier this year, also of a heart attack.

Though the show aired before my time, I used to watch re-runs on late night TV.

Horshack was best known for this:

Let's also take a moment to remember his stint on Celebrity Boxing, where he battled Dustin Diamond (aka Screech from 'Saved by the Bell').

Amazing.

Did you watch 'Welcome Back, Kotter'?