Niedermayer's horse, Trooper, was portrayed by Junior, who subsequently appeared in The Black Stallion (1979) as the horse Napoleon.
# In the final climax of interrupting the parade, this whole sequence was brought to the Universal back lot. At the time this section of the back lot had been used several times over. However, the section of road the parade ends up at is the same section that Robert Zemeckis used for the clock tower sequence in _Back To The Future (1985)_. Every angle of this street is used, but never once do you see the front of the clock tower set. The only time you do see the tower is from the back end.
According to actor James Widdoes ("Hoover"), none of the seven principal Delta actors (John Belushi, Tim Matheson, Peter Riegert, Tom Hulce, Stephen Furst, Bruce McGill, or Widdoes himself) had ever belonged to a college fraternity.
The Delta actors partied together every night but John Landis kept John Belushi away from them by having him stay in a house miles away with his wife, Judy. Belushi was a notorious partier and Landis wanted him to stay clean throughout the shoot. Belushi did host a few parties at the house but stayed clean because he saw the film as a great opportunity for him.
The scene in which Bluto smashes a bottle over his head to cheer Flounder up took 18 takes because Furst kept laughing.
Ivan Reitman wanted to direct but the studio wanted a more experienced director. Richard Lester and Bob Rafelson were approached before Landis was hired.
# # Originally, Harold Ramis and Doug Kenney's idea was titled "Laser Orgy Girls", a comedy about Charles Manson as a high school student. Producer Matty Simmons suggested that the setting be changed to college and the content to be toned down. Ramis also incorporated ideas from an earlier treatment he wrote titled "Freshman Year" based on his experiences in college.
All of John Belushi's behavior in the cafeteria was improvised. He was not told to pile all the food on his tray and when he did the director urged the camera operator to "stay with him." The infamous "zit scene" was also improvised. The reaction from the cast is genuine.
After the first day's shooting of the homecoming parade, there was a heavy rain that night. The next day, the production crew rented a field-burning tractor that shot flames across the width of the street to dry it.
Chris Miller based the character of Pinto on himself. Dean Wormer was based on Richard Nixon and Miller's Dean at Dartmouth.
To prepare for their roles, the actors playing the Deltas went to a real frat party at the University of Oregon's SAE house (except Belushi who was working on "SNL" that night). The real fraternity members did not like the actors being there and a brawl ensued. When John Belushi returned to the set and heard about the fight, he had to be physically restrained from seeking revenge.
The actors who played the Deltas harassed the actors who played the Omegas off-screen as well to keep up the feelings of animosity between their characters. Mark Metcalf changed his hotel room to the one above Bruce McGill's where the Delta actors partied every night so his anger at their noise would help him get into character.
# # A scene featuring Otter driving a girl (played by location scout Katherine Wilson) to the Rainbow Motel on Old Mill Road is seen briefly in the original trailer but was deleted from the film.
Producer Matty Simmons, founder of the National Lampoon, contributed one line to the script: Bluto's "Seven years of college down the drain!"
Mark Metcalf originally auditioned for the part of Otter.