At a 1962 college, Dean Vernon Wormer is determined to expel the entire Delta Tau Chi Fraternity, but those troublemakers have other plans for him.
Faber College has one frat house so disreputable it will take anyone. It has a second one full of white, anglo-saxon, rich young men who are so sanctimonious no one can stand them except Dean Wormer. The dean enlists the help of the second frat to get the boys of Delta House off campus. The dean's plan comes into play just before the homecoming parade to end all parades for all time.
Delta Tau Chi fraternity at Faber College is the bane of Dean Vernon Wormer's existence. It's members don't attend class, are the source of endless pranks on campus and have broken every rule imaginable. As a group, they have a negligible GPA and their main reason for living is to party. When Wormer finally finds a way to expel them all, the men of Delta Tau Chi decide to give the college a homecoming parade they will never forget.
Delta Tau Chi is the most anarchic fraternity on the Faber College campus. Its students have the worst grades and the fraternity is often a source of embarrassment to the college. Egged on by a rival fraternity, Dean Vernon Wormer is determined to shut them down. All he needs is an excuse.
1962. Friends and roommates Larry Kroger and Kent Dorfman, having just entered their freshman year at Faber College, are looking to join a fraternity. Being part of the "out" crowd (as they are referred by one "it" girl as a wimp and a blimp respectively), they are only accepted by Delta Tau Chi, arguably the worst fraternity on campus, and Kent only because he is a legacy. Despite Robert Hoover being the chapter president, its leader is Eric Stratton - "Otter" - the ladies man of the group. Otter has as his 2IC Donald Schoenstein - "Boon" - whose supportive girlfriend Katy doesn't much like the fact of Boon, Otter and the others' idea of a good time being to get constantly drunk. At the bottom of the Delta barrel is John Blutarsky - "Bluto" - the chief troublemaker with a 0.0 GPA. Within the Delta environment, Larry and Kent - renamed "Pinto" and "Flounder" respectively by the fraternity - blossom socially as much as they can by being accepted for who they are, but end up being sucked into the goings-on for good or bad of their fraternity brothers. The college's dean, Vernon Wormer, with the help of the stuck up members of Omega Theta Pi led by preppy Greg Marmalard, has vowed to find some way to revoke Delta's charter and expel its members for what seems to be their joy at and singular goal of disrupting life on campus in any way they can. Their general battles take on personal undertones with the involvement of a few women: Mandy Pepperidge, Greg's girlfriend who isn't as innocent as she likes to appear; southern belle Babs Jansen, Mandy's sorority sister who is in love with Greg and thus will willingly throw Mandy under the proverbial bus to get into Greg's heart and pants; and Marion Wormer, the Dean's bored wife. Throughout the battle, the ultimate question becomes which side will have the final move to trump all others.
Without a doubt, the raunchiest and most riotous fraternity at Faber College is by far the Delta Tau Chi House, where guys like Otter, Boone, Hoover, D-Day and Bluto, fight for their right to party. Between secret initiation rites and no-holds-barred toga parties, the perpetual Delta students have simply no intention of leaving this idyllic place on earth, nevertheless, the snotty Omegas and Dean Vernon Wormer are about to end the party, putting the Deltas on probation. Of course, when the Dean who secretly wants to expel the boys once and for all succeeds, all hell will break loose in an outrageous grand finale full of chaos, explosions, and above all, justice.
- In 1962, college freshmen Lawrence "Larry" Kroger (Tom Hulce) and Kent Dorfman (Stephen Furst) seek to join a fraternity at Faber College. They visit the prestigious Omega Theta Pi House's invitational party, but are not welcomed there. They then try next door at Delta Tau Chi House, where Kent's brother was once a member, making Kent a "legacy." There they find John "Bluto" Blutarsky (John Belushi) urinating outside the fraternity house. The Deltas "need the dues" so they permit Larry and Kent to pledge. They receive the fraternity names "Pinto" (Larry) and "Flounder" (Kent).
Vernon Wormer (John Vernon), dean of Faber College, wants to remove the Delta fraternity from campus due to repeated conduct violations and low academic standing. Since they are already on probation, he puts the Deltas on something he calls "double secret probation" and orders the clean-cut, smug Omega president Greg Marmalard (James Daughton) to find a way to get rid of the Deltas permanently.
Flounder is bullied by Omega member and ROTC cadet commander Doug Neidermeyer (Mark Metcalf), so Bluto and Daniel Simpson "D-Day" Day (Bruce McGill) persuade Flounder to sneak Neidermeyer's horse into Dean Wormer's office late at night. They give him a gun and tell him to shoot it. Unbeknownst to Flounder, the gun is loaded with blanks. Unable to bring himself to kill the horse, he fires into the ceiling. The noise frightens the horse so much that it dies of a heart attack.
In the cafeteria the next day, smooth-talking Eric "Otter" Stratton (Tim Matheson) tries to convince the stuck-up Mandy Pepperidge (Mary Louise Weller) to abandon her boyfriend, the uninteresting Marmalard, and date him instead. Bluto proceeds to provoke Marmalard with his impression of a popping zit by stuffing his mouth with a scoop of mashed potatoes and propelling it at Marmalard and table mates, Chip Diller (Kevin Bacon) and Barbara "Babs" Jansen (Martha Smith). Bluto then starts a food fight that engulfs the cafeteria.
Bluto and D-Day steal the answers to an upcoming psychology test, but it turns out the Omegas planted the exam stencil and the Deltas get every answer wrong. Their grade-point averages drop so low that Wormer needs only one more incident to revoke the charter that allows them to remain on campus.
To cheer themselves up, the Deltas organize a toga party, during which Otis Day and the Knights perform "Shout". The dean's alcoholic, lecherous wife, Marion (Verna Bloom), attends the party at Otter's invitation and has sex with him. Pinto hooks up with Clorette (Sarah Holcomb), a girl he met at the supermarket, and makes out with her only to learn she is the mayor's 13-year-old daughter. He later takes her home in a shopping cart. Due to the party, Wormer organizes a kangaroo court with the Omegas and revokes Delta's charter and all belongings are confiscated.
To take their minds off their troubles, Otter, Donald "Boon" Schoenstein (Peter Riegert), Flounder and Pinto go on a road trip. Otter picks up some girls from Emily Dickinson College by pretending to be the fiancé of Fawn Liebowitz, a girl who recently died on campus. They stop at a roadhouse because Otis Day and the Knights are performing there, not realizing that it caters to an exclusively black clientele. The hulking patrons intimidate the guys and they flee, damaging Flounder's borrowed car and leaving their frightened dates behind.
Boon breaks up with his girlfriend Katy (Karen Allen) after discovering her sexual relationship with a professor (Donald Sutherland). Marmalard is told that his girlfriend is having an affair with Otter, so he and other Omegas lure him to a motel and beat him up. The Deltas' midterm grades are so poor that an ecstatic Wormer expels them all. He even notifies their draft boards of their eligibility. In the process, before Bluto attempts to speak to the dean, Wormer orders Flounder to speak with the words, "Well? Out with it!", whereupon Flounder vomits on the dean.
It seems time for the Deltas to give up, but Bluto, supported by the injured Otter, rouses them with an impassioned, historically inaccurate speech ("Was it over when the Germans bombed Pearl Harbor?!") and they decide to take revenge on Wormer and the Omegas. The Deltas construct a rogue parade float with Flounder's car as its base and wreak havoc on the annual homecoming parade. During the ensuing chaos, the futures of many of the main characters are revealed. The last shot of the film is of Bluto driving away in a white convertible with his soon-to-be wife, Mandy Pepperidge.