Plot of I Love You, Man :
Peter Klaven (Paul Rudd), a big-time real estate salesman, just got engaged to Zooey Rice (Rashida Jones). Zooey is ecstatic about the engagement and calls her friends to tell them about it, but Peter does not seem to have anyone special he'd like to share the good news with. While visiting his parents' (J.K. Simmons and Jane Curtin), it comes out that Peter is actually a "girlfriend guy," and his male friends when he was growing up "fell by the wayside." After overhearing Zooey's friends tell her that they are concerned Peter does not have any friends, Peter realizes he needs to find some male friends in order to have a best man for his wedding. Peter seeks the advice of his younger, gay brother Robbie (Andy Samberg) on how to meet platonic guy friends and how to take them on "man-dates".
Peter's first attempt is to hang out with Barry (Jon Favreau), who is married to Zooey's best friend Denise (Jaime Pressly), for poker night with the guys. It ends horribly when, after chugging too many beers, Peter projectile vomits all over Barry, who already dislikes Peter to begin with. Robbie then sends Peter out with a guy from his gym for a soccer game. That does not last long, since the man angers fans at the game and has a very high-pitched voice. Peter seeks friends online and finds Mel, who represented himself as a young man on his online profile, but is actually an old man. Peter's mother tries next by sending him to dinner with a man named Doug Evans (Thomas Lennon) who just moved to L.A. Against Robbie's advice, Peter goes to dinner with Doug, who believes it to be a romantic date and gives Peter a French kiss.
With all these failed attempts, Peter decides to give up, but during an open house at Lou Ferrigno's property, he meets Sydney Fife (Jason Segel). They instantly hit it off when Sydney gives a play-by-play of a potential buyer passing gas. The two men exchange business cards. When Peter calls Sydney he leaves a very embarrassing voice mail, but when Sydney calls him back they decide to go out for drinks.
After a fun night out, they hang out again for lunch and afterward Sydney shows Peter the "man cave," a space in his garage where he keeps a big-screen TV and his collection of rock instruments and Rush memorabilia. They start playing musical instruments together and hanging out a lot more. Peter finally introduces Sydney to Zooey at their engagement party. At first, it goes well, and Zooey thinks Sydney might hit it off with her perpetually single friend Hailey. But her opinion of him sours when Sydney makes a very awkward speech hinting that Zooey needs to give Peter more oral sex.
Peter convinces Sydney to go golfing with the girls and it ends with Hailey storming off the green. Right after that, when Peter is supposed to be watching TV with Zooey, Sydney calls and talks Peter into going to see Rush instead. At the concert Zooey feels ignored while Peter and Sydney are really enjoying the concert. During tuxedo shopping, Sydney asks Peter why he is marrying Zooey and asks Peter for an $8,000 loan. Doug coincidentally shows up and confronts Peter, making a scene because he thinks he is with Sydney. Peter finally comes clean to Sydney telling him that he was searching for friends before meeting him and that he will loan him the money.
Zooey, however, is now suspicious of Sydney, especially after he gets in a fight with Lou Ferrigno, possibly causing Peter to lose exclusive sales rights to Ferrigno's house. Peter tells Zooey that he lent Sydney money and asks her if she knows why they are getting married. Hurt and angry, Zooey leaves to stay at Denise's house.
When Peter leaves for work that next morning he sees several embarrassing billboards advertising his real estate business that Sydney put up using his loan. When he confronts Sydney, he decides to end their friendship. After he patches things up with Zooey, explaining to her that he is nervous but ready to get married, Peter discovers that the ads worked; he starts receiving more clients, including an apologetic Doug, and offers on the Ferrigno house.
While Peter feels bad about fighting with Sydney now that the Ferrigno house is sold, he doesn't re-invite Sydney to the wedding. Before the wedding, Zooey sees Peter upset, so she calls and invites Sydney (who is already on his way) to the wedding. Just before the vows are to be taken, Sydney makes a dramatic entrance, they declare their platonic love to each other, and Sydney assumes the role of best man.
article source : wikipedia
