NOTE: This spoiler was sent in by Monica.

Gary (Vince Vaughn), an affable tour guide in Chicago, is at a Cubs game with his buddy Johnny (Jon Favreau) when he spots Brooke (Jennifer Aniston) a few seats down. She's with a dorky, plaid-shorted date and doesn't look like she's having a lot of fun. Gary thinks she's cute, so he buy's her a hot dog and convinces her to leave her lame date and come out with him.

The next sequence is a series of still photos of Gary and Brooke's courtship. We find out that they go to football games, barbecue with friends, join a couples bowling league, buy a condo together—and look pretty happy together doing it.

Flash forward two years. Brooke and Gary are living together. Gary’s still a popular tour guide for a company he owns with his two brothers; Brooke works at an art gallery. On this particular day, Brooke is assisting a very attractive male customer who ultimately decides not to buy anything. She tells him to wait until he sees something he just has to own. The day ends and Brooke rushes home, seeming stressed out.

We find out that Brooke is stressed because she and Gary are having both of their families over for dinner. The families haven’t spent a lot of time together, so Brooke really wants this to go well. Gary wanders in the door and hands Brooke a small bag of three lemons. She’d asked him to pick some up on his way home and he’s proud that he remembered. But it turns out that Brooke needed 12 lemons for dinner, and Gary’s forgetfulness feels like a slap in the face. Brooke tries to get Gary to take a shower and then help her in the kitchen, but Gary says he’s tired after a long day and just needs to relax. Brooke says that she’s had a long day at work too, but she still came home, cleaned the apartment, and cooked dinner. They argue for a bit and then the doorbell rings. Brooke asks Gary to answer it, but at that moment he decides he needs to take a shower, so he leaves Brooke to deal with the arriving guests.

Dinner is awkward. The families are very different, but they make an effort. We discover that Gary and his brothers, the nerdy Dennis and the lecherous Lupus, want to expand their tour bus company to include sea and air travel. Brooke’s brother, the ambiguously gay and insanely peppy Richard, tries to lead the whole table in a song.

Post-dinner, the couple is exhausted, but Brooke wants to clean up right away because she hates waking up to a messy house. Gary says he’s still not had a chance to relax and he’s rather play video games. Finally he feels so nagged by Brooke that he agrees to help, but Brooke says that’s not the point. She doesn’t want him to help because she’s nagged him, she wants him to help because he appreciates what she does for him and he wants to do things for her too.

This turns into a blow-out argument about their relationship. Brooke says that Gary is selfish and that they always do what he wants. They never go to the ballet, they never travel, they never pursue her interests. Gary says he wishes she’d stop berating him and just leave him alone. Brooke says that he just got his wish. She’s leaving him completely alone and they’re breaking up. Gary storms out to go visit Johnny at his bar, Brooke phones her best friend, Addie (Joey Lauren Adams). Both friends agree that their respective buddies did the right thing. And so, while both Brooke and Gary expect the other to apologize, neither one does. Instead, Gary ends up sleeping on the couch. Instead of recognizing that this might have been a stupid argument that got out of control, they’re really broken up.

Over the next few weeks, Brooke and Gary both show glimpses of wanting to get back together, but neither one wants to be the one who apologizes. Instead, they resort to sophomoric tricks hoping to make the other see the light. Brooke’s boss advises her to parade around the condo naked so Gary can see what he’s missing. Brooke also goes out on a series of dates with other people to make Gary jealous. Gary, on the other hand, holds a strip poker party in the condo, inviting over attractive women to play.

It’s clear that things have gotten really out of hand. Brooke has Gary voted off their couples bowling league. Meanwhile, the condo is looking like a pig sty. Brooke wasn’t kidding—when Gary doesn’t have her taking care of things, everything’s a mess. One night, they have a big argument in front of their friends. Their mutual buddy (and real estate agent), Riggleman, says that he hates to say it, but he really thinks they should sell the condo and find their own places before things get even worse. They agree.

One evening, Brooke gets a message from Riggleman that the condo’s been sold. This makes her realize how out of control things have gotten and how much she misses Gary, so she decides to try and make nice. She tells him that she has tickets to a band he likes—she’d bought them months ago as a surprise. She asks if he’d like to go with her, He says that would be nice, and she says she’ll leave his ticket at will-call.

Fast-forward to the concert. Brooke’s there, but she’s alone. Gary never shows up. She’s heartbroken. She feels like Gary never realizes how much she does for him, and he never puts her first the way she does for him. Gary arrives home and offers to pay for the ticket he didn’t use. He obviously didn’t realize what a big deal this was to Brooke, and is distraught when he realizes how upset she is. Brooke tells him exactly how under-appreciated she’s felt. Gary starts to apologize, but Brooke asks him to just leave. Gary goes to Johnny’s bar, and Johnny tells him that Brooke is right. The relationship has been on Gary’s terms. Brooke does all kinds of things for Gary, and Gary takes all of it for granted.

The next night, Gary’s determined to make it up to Brooke. He cooks her a nice dinner (the first time he’s ever cooked for her) and cleans the condo. Instead, she arrives home with the hot guy from the first scene in the art gallery. Gary pulls her aside and says that he’s thought about what she’s said and realizes that she was right. Brooke says it’s just too little too late. She’s realized that for her, it’s over. Gary assumes it’s because she’s dating the hot guy, but once Gary leaves we realize that the guy is only there because he’s buying a piece of art from Brooke. Incidentally, it’s a piece of art that Gary has always hated.

A few days later, the condo’s empty. Brooke and Gary are moving out, and both admit to each other that there are lots of things they would have done differently. Gary would have been more appreciative and taken Brooke to the ballet. Brooke wouldn’t have been so anal and would have let Gary have the pool table he always wanted. But it’s too late, and so they turn in their keys and say goodbye.

The last scene takes place two years later. We see that Gary has become more responsible, and his business has taken off—they now have boat tours as well. While walking home from work he runs into...Brooke, who’s just recently gotten back into town after spending a long while traveling. They chat for a few minutes and agree they should get together soon. When they part ways, both of them turn back to smile at each other several times and we get the impression that it might not be over for them after all.

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Brook (Jennifer Aniston) dates other guys to make Gary (Vince Vaughn) jealous.  It doesn't work. 

By the time he realizes that she's the one for him, it's too late because she tells him she doesn't feel the same way. 

They sell the condo.  He expands his family business and she travels. 

Months later, they run into each other and greet each other but gaze at each other like they "miss" each other.  They say hello, compliment each other and agree to not let so much time pass on before keeping in touch.  As they walk in opposite directions, they both look back.  Gary winks at Brook and she smiles back.