Of all the animals in Animal House, John Belushi’s Bluto was the most out-of-control. By reputation, Belushi had the same standing among the classic comedy’s cast. But according to Tim Matheson, the actor who played Delta Tau Chi president Eric “Otter” Stratton, Belushi was professional and sober for the film’s production.

“Belushi, for the record, was clean on set during Animal House,” Matheson writes in his new book Damn Glad to Meet You: My Seven Decades in the Hollywood Trenches, per People. “If he did anything, it was away from the rest of us, and he never gave any signs he was up to anything.”

After all these years, Belushi is the star Matheson gets asked about the most, “and I've worked with almost everyone,” he says. At least when it comes to Animal House, the memories are good ones.

Animal House director John Landis made it...