The movie beings with Eugene Pratt (Zach Cregger) and Tucker Cleigh (Trevor Moore) as little kids. Tucker wants to go and see Eugene's brother's rare baseball collection so they go inside Eugene's brothers closet and steal the box. Inside, they also find a playboy magazine. Eugene is disgusted by the site but Tucker is fascinated and curious, asking questions like "Where do they pee out of?" Tucker leaves the room with the magazine. Three weeks later, Tucker is checking out the ass of another girl and making sexual remarks like a teenage pervert while Eugene looks on in disgust.

Fast forward about eight years. Eugene and Tucker are 18 years old and about to graduate. Little has changed though as Tucker continually checks out girls and makes perverted remarks while Eugene is still disgusted and tells Tucker to cut it out as he now has a girlfriend and feels uncomfortable checking out other girls. Candace walks by and Tucker makes a sexual joke about her epilepsy, causing her to beat him up.

Eugene goes to speak at an assembly with his girlfriend Cindi Whitehall (Raquel Alessi) while Tucker watches in the crowd. They inform the middle school kids listening that they are abstinent and they are trying to encourage everyone to be abstinent to prevent the spread of STD's. Eugene tells them about his brother who had sex too early and got an STD as a result and then shows them a picture of it, horrifying the kids.

Later that night, Eugene climbs up a tree and sits outside Cindi's window and proclaims his love for her. He then suggests they go to a party after prom to have fun. Cindi casually asks if this means that they are finally going to have sex but Eugene firmly states no, saying that he does not want the same thing that happened to his brother to happen to him. Cindi looks disappointed but agrees. Eugene then realizes his mistake and calls her and promises her that they will have sex at the party. 

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