Among the "sweathogs"—the name given in the series to the recalcitrant students put in the care of Gabe Kaplan, who played teacher Kotter—Horshack was the most mild. He frequently raised his hand with a vehement nasal "Ooh! Ooh!" to answer a question, and honked out a stop and start laugh to Kotter's awful jokes.

Mr. Palillo was predeceased by Robert Hegyes, who played fellow student Epstein. Like Hegyes, Mr. Palillo was so identified with Horshak that the remainder of his acting career suffered once the series ended in 1979.

Ron Palillo was born on April 2, 1949, in Cheshire, CT. He became involved in high school theatre as a way of managing his stuttering, according to the New York Times. Soon after graduating from college, he was cast as an understudy in Lanford Wilson’s Off-Broadway play Hot L Baltimore. While doing that role, he was cast as Horshack.

Following years of infrequent work, he moved to New York in 1991. He acted in runs of The Fourposter at Shadowland Theatre of Ellenville, and Sarasota, FL's Golden Apple Dinner Theatre. He was cast in the daytime drama "One Life to Live" for a year and won the lead role in an Off-Off-Broadway production of Amadeus. In 2010, in West Hartford, CT, he directed the first production of The Lost Boy, a musical he wrote based on the life of J. M. Barrie.

In 2009, he starred in the Ivoryton Playhouse production of the Frederick Knott thriller Wait Until Dark. His survivors include his partner of 41 years, Joseph Gramm, as well as two brothers and a sister. His mother died last year.