Danny and Wheeler are salesmen who promote an energy drink called "Minotaur", ostensibly to encourage school kids to stay off drugs. While Wheeler loves the job, Danny views it as a pointless, dead-end job, causing him to be depressed and jaded. Danny's uncouth behavior also results in the collapse of his relationship with his girlfriend Beth, who breaks up with him after he impulsively proposed to her. After an awry presentation at a high school, the duo find their Minotaur truck being towed, as they were parked in a no-parking zone. Danny drives their truck free of the tow truck, damaging it and nearly running over a security guard and crashing into a statue. Danny and Wheeler are arrested and charged with assault and disorderly conduct.
Beth strikes a deal with the judge in which the guys have to log 150 hours of community service over the next 30 days, in lieu of 30 days in jail. They are to complete their service with Sturdy Wings, a big brother-big sister program led by Gayle Sweeny, a recovering addict. Gayle is aware of their court mandate and warns them that if they fail to meet her requirements they will be sent to prison. Wheeler is paired up with Ronnie Shields, a vulgar young boy who has driven away all the other "Bigs" he has been paired with. Danny is assigned Augie Farks, a shy teenager obsessed with medieval live action role-playing games.
Danny is unable to find common ground with Augie, while Ronnie takes a disliking to Wheeler. Danny considers giving up and choosing the jail sentence, but Wheeler insists that if they go to jail, they will get raped. They gradually bond with their "littles"; Ronnie and Wheeler share the experience of having been abandoned by their fathers, while Danny learns about Augie's medieval fantasy realm. Ronnie takes an interest in Wheeler's favorite band, Kiss, and discovers that Wheeler shares his obsession with female breasts, which Wheeler teaches him to control. Danny and Augie bond when they realize that they are both involved in the Sturdy Wings program against their will. Danny joins Augie's live action role playing game Live Action Interactive Role-playing Explorers (LAIRE) and unsuccessfully reconciles with Beth, who explains she must commit to the break-up because "it is for the best".
However, their good luck is short-lived. When Augie manages to sneak up on the King of LAIRE, Argotron, the King lies and tells everyone that he killed Augie. Defending Augie, Danny confronts and shoves the King, getting Augie and himself banned from LAIRE permanently. Later, Danny insults Augie's mother and her boyfriend for refusing to support Augie's hobby, earning their hatred. As soon as Augie's parents kick Danny out of their house, Danny retorts, "I'd be psyched if he was my kid." Meanwhile, Wheeler takes Ronnie to a party and leaves him unsupervised, resulting in Ronnie walking home alone and a series of angry messages from Ronnie's mother, Karen, on Wheeler's cellphone. Ronnie and Augie's parents ask Sturdy Wings for new mentors, and Danny and Wheeler are expelled from the program, thus failing to complete their community service. Beth says that she will defend Danny and Wheeler in court, but cannot make any promises, as they will most likely be sent to jail. Danny and Wheeler argue and go their separate ways.
Danny convinces King Argotron to allow himself and Augie to fight in the much-awaited battle royale. Wheeler gets permission from Karen to hang out with Ronnie after he gets out of jail, and earns Ronnie's forgiveness. However, the King secretly warns the other members of Augie's LAIRE "country" of Xanthia that allowing Augie to fight with them will lead to severe retribution in the game. They call Augie to tell him he is too much of a liability and he has nowhere to turn. To form a new LAIRE country, Danny and Augie need four members and matching costumes. Danny asks Wheeler and Ronnie to join them. They arrive with Wheeler's Kiss costumes and a Kiss-themed Minotaur truck, naming their new country "Kiss-My-Anthia". After a betrayal by his former Xanthian allies, Augie finally duels with the king, defeating him. Sarah, a hidden player who goes by Esplen in LAIRE, attacks and defeats Augie; she is crowned the new queen and chooses Augie as her king-consort. Augie's parents forgive Danny.
Impressed with having seen that Wheeler and Danny care for the children, Gayle clears their names with the judge. Danny serenades Beth with a rendition of the Kiss song "Beth" and they happily reconcile.
Seann William Scott as Wheeler
Paul Rudd as Danny
Christopher Mintz-Plasse as Augie
Bobb'e J. Thompson as Ronnie
Elizabeth Banks as Beth
Jane Lynch as Gayle
Ken Jeong as King Argotron
Kerri Kenney-Silver as Lynette
Ken Marino as Jim
Nicole Randall Johnson as Karen
A.D. Miles as Martin Gary
Joe Lo Truglio as Kuzzik
Vincent Martella as Artonius
Matt Walsh as Davith of Glencracken
Allie Stamler as Sarah/Queen Esplen
Jessica Morris as Linda the Teacher
Carly Craig as Connie
Keegan-Michael Key as Duane
Amanda Righetti as Isabel
Jorma Taccone as Mitch from Graphics
Armen Weitzman as Party Dude
Elijah Polanco as Ronnie's Friend
Nate Hartley as Rule Master
Louis C.K. as School Liaison