In fact, Landis actually knew Bernstein when he was a kid, and had actually gone to school with his son, Peter.
Defictionalization: DeWayne Jessie, the actor who played Otis Day, changed his name and recorded with the Knights.
Executive Meddling: Various. Universal President Ned Tanen insisted the Road Trip sequence be cut because he worried it could start race riots. Landis showed the clip to Richard Pryor, who wrote to the executive "Ned, Animal House is fucking funny and white people are crazy - Richard."
D-Day is played by veteran character actor Bruce McGill, who played Jack Dalton on MacGyver, was the voice of Cleveland's racist, lecherous, closeted gay boss Lloyd Waterman on The Cleveland Show (sounds hard to believe? Here's some video evidence), and is currently in the TNT drama Rizzoli and Isles.
Throw It In: When Bluto is sneaking around the campus at night and slips, rolls around and casually stands back up, that was an actual slip-up by Belushi from the very wet grass on the location. The director thought it was the funniest take and used it.