'Welcome Back, Kotter' star Ron Palillo died early Tuesday in Palm Beach, Fla., after suffering a heart attack in his sleep. He was 63.
Palillo was known as class clown Arnold Horshack on the hit 1970s sitcom. A member of the Sweathogs with a young John Travolta, he was known for calling out "Ooh ooh ooh, Mr. Kotter" and his wheezing staccato laugh.
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Palillo was found at about 4:30 a.m. by his longtime companion, Joseph Gramm, TMZ reported.
A heavy smoker, he was rushed to a local hospital but pronounced dead on arrival, according to People.com.
“He just couldn’t have been more fun and intelligent or talented. He was an amazing human being,” longtime friend Stacy Sacco told Orlando, Fla., TV station WPTV. “I had been a fan. We all knew who he was. He was a shining star."
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A Connecticut native, Palillo co-founded a community theater at just 14 and began acting professionally shortly after college.
He starred in "Welcome Back, Kotter" from 1975-79 and guest-starred on several popular programs in the 1980s, including "The A-Team" and "CHiPs," according to Entertainment Weekly.