In fact, Landis actually knew Bernstein when he was a kid, and had actually gone to school with his son, Peter.
The Danza: John Belushi as John "Bluto" Blutarsky.
Subverted, however, with John Vernon's character Vernon Wormer, the dean of the college. According to John Landis, his first choice for the role was Jack Webb, who turned it down because he felt that the film was making fun of his straight-laced, law-and-order image.
Doubly subverted with John Vernon, as Vernon was actually one of his middle names. He was born Adolphus Raymondus Vernon Agopsowicz.
Dawson Casting: Most of the cast. For example, Mark Metcalf (Neidermeyer) was 32.
Defictionalization: DeWayne Jessie, the actor who played Otis Day, changed his name and recorded with the Knights.
When not filming, John Landis purposely prevented the actors playing Deltas from interacting with the actors playing Omegas so that the "enemies" wouldn't end up bonding with each other (the Delta actors were even brought to the set a few weeks earlier than the Omegas to achieve this).
As a mark of the success of Landis' plan, Bruce McGill, who played D-Day, had the piano at the hotel accommodating the cast moved to his room and held late night parties with the other Delta actors; Mark Metcalf, who played Niedermeyer, had his room changed to the one above McGill's so that the noise and resulting sleep loss would keep him in a bad mood for filming.
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 Shownote (sounds hard to believe? Here's some video evidence), and was on 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.