NOTE: This spoiler sent in by L who says... This was adapted from a marginally funny book but the movie managed to cut all the parts that made the book funny.
Denis Cooverman is valedictorian and goes to the podium to make his speech. He deviates from his intended speech in order to take the time to say something he feels is worth saying. He insults the class bully, a stuck up girl who thinks she’s all that and several other people (including his best friend Rich Munsch, who he implores to come out of the closet). He ends his speech by declaring his love for the head cheerleader, Beth Cooper.
After his speech, Beth approaches him during the reception and tells Denis that he embarrassed her. He apologizes but she tells him that it was sweet. He impulsively invites her to a party at his house that night, and she tells him that she might stop by. Beth’s ROTC boyfriend, whom Denis insulted in his speech, tries to intimidate Denis from across the room with his friends. Rich approaches Denis and admonishes him for saying that his best friend is gay. Rich is adamant that he isn’t, but is impressed that Denis invited Beth to the party.
After the ceremony is the “party.” Denis’s parents leave him and Rich in the house and let them do whatever it is they want to do. Rich gives Denis some condoms and begins spouting movie references when there is a knock at the door. Beth arrives with her two friends, Treece and Cammy. Cammy and Treece are bored and only came because Beth said it might be fun. Cammy is a pretentious tool and Treece is the school slut.
In order to entertain the guests, Denis busts out the champagne. However, he ends up shooting himself in the eye with the cork. This earns Beth’s pity, but once she notices the condom that fell onto the floor she starts to make an excuse to leave. It becomes clear that Beth was trying to get away from her boyfriend Kevin. He shows up, prepared to beat the crap out of Denis.
Denis locks the front door in a desperate attempt to stay alive. However, Kevin walks in through the backdoor with his military friends and starts trashing the house in his attempt to throttle Denis. Denis makes it up to his room (where a blown up poster of Beth is pinned above his bed) where he draws a replica light saber in order to defend himself. Kevin destroys the blade and Denis ends up jumping out of the window to escape. He sees Rich, Beth, Treece and Cammy pile into Beth’s car and joins them.
Rich is excited by the recent turn of events and tries to cozy up to the women. However, they won’t have any of it and refer to him by his nickname “Dick Muncher.” The girls think they should get trashed so they go to a liquor store to buy liquor. Beth goes inside to make the purchase and Denis tags along.
Inside the liquor store, Denis and Beth collect some liquor and make awkward small talk. Beth then takes the liquor to the front desk to pay for it, but the clerk rejects her mother’s ID because Beth doesn’t look as old as her mother. So Beth improvises and promises to kiss the clerk in order to get the beer. He accepts and Denis is left in shock.
The group, now fueled with liquor, drives around town and drink at an isolated section of town. Beth and Denis talk while Treece, Cammy and Rich try to tip a cow. Rich ruins his expensive shoes and Beth won’t allow him to take them in her car. Rich sadly abandons his shoes and the crew drives away. As Beth drives the car, Denis notices that there is a slight tear in her eye. However, as they drive they crash into a car. They speed away, leaving Denis’s parents (who were hooking up in the car) perplexed as to who hit them.
Beth decides that since it’s graduation night and she still has the head cheerleader’s key they should break into the school. They park out front and the girls, drunk, decide that they should show their “act” to the boys. Rich is instantly excited by this and follows them to the girl’s shower. Denis lags behind, not sure if it is a sincere invitation (and also struggle to come to terms with the differences between the real Beth and the one he worshiped in his mind).
Denis arrives at the girl’s showers as the girl’s cover themselves with towels. Beth sees that Denis is looking, so she walks over and drops her towel in front of him. The girls then go frolic in the showers but before Denis can join them, Kevin arrives.
Kevin is about to finish what he started at Denis’s house when Rich pulls a wet towel and attacks Kevin and his ROTC goons. A flashback reveals that Rich was once severely injured during a wet towel beating after gym class. He trained and trained in the art of towel whipping so that he would never fall victim to wet towel aggression ever again. He uses his skills to keep Kevin and his men at bay. He tells Denis to run and Denis reluctantly abandons his friend.
Denis meets the girls at Beth’s car and complains that they should wait so that Rich can catch up. However, Beth notices that a police car is outside investigating the unauthorized entry to the school. She’s about to tell Denis that it’s every man for himself when Rich opens the door and tells them to drive. Kevin and his friends are arrested for trespassing, while Denis and the others slowly drive off.
As Beth drives, she flips on Denis when he attempts to be a back seat driver. Denis is bleeding from Kevin’s beating so Treece gives him a pair of tampons to clog his nose. The group decides that they need to hide from the cops, so Beth drives to Treece’s father’s cabin. Denis is dejected and Beth tells him that it’s not a big deal. She tells him that the group decided that going to Denis would be funny and that was the only reason they went to his “party” earlier.
Beth sees that Denis’s shirt is soaked, so she tells him to take of the shirt so that she can dry it off. She holds it outside the window, but it gets blown away. Beth stops the car and Denis goes to recover his shirt. A raccoon claims the shirt and starts eating it. Denis tries to take the shirt back but the raccoon screams at him and he ends up abandoning the shirt. Beth laughs and gives Denis her poncho and tells him that it’s her favorite poncho.
At Treece’s cabin, the group breaks out champagne and start drinking. After a while, Beth grows bored and asks if anyone wants to watch the sunrise with her. Denis decides to join her, and they end up walking on the beach. Denis asks if she has any family, and Beth tells her about her older brother, who got sick and died while she was a toddler. She explains that while Denis is going to a good school and has potential, Beth has no chance of leaving the town. The pair then proceeds to make out.
Back at the cabin, Treece and Cammy proceed to ridicule and question Rich’s sexuality. Rich holds his own and insists that he is not gay. The ladies decide that they should have a little experiment. Treece grabs a condom and the group has a threesome. Afterward, the three all have an awkward look on their face. Rich proved he wasn’t gay, but it seems that Treece and Cammy used the opportunity to experiment with each other.
Later the next day, Beth drives everyone. They pull up to Denis’s house as Denis’s parents assess the damage to the house. They recognize Beth’s car as the one which hit theirs. They ask Denis what happened but all he does is tell them he’s fine.
Mrs. Cooverman doesn’t press the issue and goes to make breakfast, after making a quip about how Beth might have done it already. Denis’s father asks how Denis should be punished, but Denis tells him it was worth it. It’s implied that he and Beth slept together, but never directly addressed. Rich says good-bye to Treece and Cammy and Beth thanks Denis for loving her. Denis and Beth kiss again and Rich and Denis start walking toward the house to get some breakfast. As they walk back, Rich tells Denis that he might be bi.
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