Danny, who owns a garage/car lot, Michael, a lawyer, and Rick, a salesman, all live together in a house in The Windy City. They all like to play practical jokes on each other, and one of them will usually say "Watch it!" when the joke is played. Into this situation comes John, Michael's somewhat estranged cousin, and a drifter. At a party Michael takes John to, John sees Anne, Michael's on-again, off-again girlfriend (Michael seems like he's the Ur-Example of I'm a Man; I Can't Help It, but in reality, he has a Freudian Excuse; see below); Anne catches Michael cheating and leaves the party, so John, who's attracted to her, follows her, and they strike up a friendship that leads to a relationship. However, John can't really commit and Cannot Spit It Out, so Michael moves in, apologizes to Anne, and they get engaged. But does he mean it? And does she still have feelings for John?
There's also the plot of the practical jokes, as well as a subplot about Rick getting into a relationship with Ellen, a schoolteacher.
This film contains examples of:
- All Girls Want Bad Boys: Discussed. This is Rick's entire theory about women. In fact, he tells John since he's a nice guy, the only women he should have anything to do with are women who have just dumped assholes, and who will therefore appreciate nice guys like John. Rick also proudly calls himself one of those assholes (though not really; see Freudian Excuse below), which is why he claims to do so well with women.Rick: I am human cocaine!
- The Baby Trap: Subverted. Ellen tells Rick she's having a baby, and it's his, but she doesn't want him involved because she thinks he's a jerk. Then it turns out to be a "Watch It" cooked up by her and John to point out to Rick he needs to grow up and be a man.
- Blatant Lies: At the party, Danny tells John he doesn't play the "Watch It" game anymore. When John goes home that night, he goes to the kitchen to fix something to eat, and the camera pans down to Danny hiding in the cabinet under the sink, waiting to grab John's leg at the appropriate time to scare him.
- Brick Joke: John takes Anne to Comiskey Park for their first date. Near the end of the movie, he gives her tickets for the last home game of the season, hoping she'll show up. She does.
- Cannot Spit It Out: The closest John gets to a declaration of love is when he tells Anne, "I don't know that I don't love you." Naturally, she's not convinced by that.
- Chekhov's Gag: At the end, we see Danny is about to use the same car gag he and Rick used on John earlier on Rick and Ellen as they're about to drive off on their honeymoon.
- Deadpan Snarker: John, Michael and Rick each have a bit of this.
- Drives Like Crazy: John, although to be fair, it's not his fault; Danny and Rick have hooked up John's car so it can be controlled remotely by phone, and Rick has all kinds of fun with that.
- Freudian Excuse: John explains to Anne that when he and Michael were younger, Michael's mother was crazy, and John's parents stepped in, adopting Michael. However, when John's mother died, his father gave Michael back to his mom. This, John explains, is the source not only of his estrangement with Michael (John promised Michael at the time he would never have to return to his mom), but also his attitude towards women.
Rick: And if you remember one thing from our conversation out here, please let it be this: The moment you start loving a woman, you can begin counting the days until that bitch walks right out the front door on you.
- Rick sort of hints at one during his speech to John about how women like Anne are only attracted to assholes like Michael:
"That's pretty well thought out... but angry Rick. Very, very angry. Who broke Rick's heart? Did somebody break Rick's heart?"
- John, of course, calls him out on this:
- I Can Change My Beloved: According to Rick, this is why All Girls Want Bad Boys, and needless to say, he mocks them for this. Ironically, it's implied Ellen ends up changing Rick by the end.
- The Immodest Orgasm: According to Rick, one of the women Michael sleeps with is like this:Michael: Was she vocal?Rick: Vocal? She should have been a carnival barker, for crying out loud!Michael: Are you telling me you weren't listening outside my door?Rick: Well, sure, to a reasonable hour, but 3 a.m? "Oh my God, Michael. Oh my God, Michael! Oh Oh OH OH OH!" I mean, what are you DOING to these girls, for Chrissakes?
- Jerk Jock: All three of the guys played baseball in college, and so they all continue to show traits of this, Michael and Rick especially. In Rick's case, however, he got better.
- My Girl Is Not a Slut: An interesting subversion; when Rick finds out Ellen hadn't slept with anyone for a long time before him, he freaks out because that shows she only sleeps with people she cares about, and he wants to keep the relationship casual. This leads to his later Jerkass behavior, before he finally gets better.
- Practical Joke: The major "Watch It!" pranks are:
- When John first gets to the house, Michael has him take all of the food out of the refrigerator, and then get in, so that when Rick opens the fridge to put beer in, John will jump out and yell, "Watch It!"
- Rick's revenge comes at the party they all go to that night; a woman comes on to John and takes him to a closet. Just as she's undressing, her boyfriend shows up yelling for her, he breaks into the bathroom, throws John out, and threatens her. However, when John kicks the door down to get back in, it turns out they were only joking.
- Late in the movie, when John decides he's had enough of Michael and leaves town, Rick, with the reluctant help of Danny, rigs John's car up so it can be controlled remotely by car phone. Naturally, the brakes, windshield, radio, trunk and other parts of the car go crazy.
- John does get his revenge, however: first, he has Ellen pretend to be pregnant to get Rick to grow up. Then, a newscast implicates Danny's partner in the garage in a stolen car ring, except it was just a ruse cooked up by John, who was pretending to be a detective. Finally, he pays a prostitute to get with Michael while he and Ann are at a concert.
- Finally, at the end of the movie as Rick and Ellen are about to drive off on their honeymoon, it looks like Danny's going to play the same car trick on Rick that Rick played on John.
- Too Much Information: As Rick is trying to explain to John that Anne is going to leave Michael and come back to him:Rick: She's gonna come crawling back, and you will finally be appreciated as the nice guy that you are. Plus, in the meantime, she will have spent time with Michael, and of course that means she will have been exposed to such a wide variety of sexual positions and perv-Danny: (interrupting) Rick! Cool it, would you? He...he gets the picture.
- Wacky Fratboy Hijinx: The "watch it" gags can be seen as an outgrowth of this, as Danny, Michael and Rick started doing them in college.