13岁的风流小子唐尼（亚当·桑德勒 Adam Sandler 饰）生性放荡不羁，抽烟酗酒不在话下，更离谱的是，他竟然与自己22岁的女老师发生了关系还使其怀了孩子，老师入狱，将孩子汉（安迪·萨姆伯格 Andy Samberg 饰）托付给了唐尼。然而唐尼依旧是那个风流少年，根本没有尽到一个靠谱父亲的责任，于是当汉年满18岁，变愤然离开了父亲。 如今42岁的唐尼已经变成一个百无聊赖的酒鬼，欠下的税还足够让他在监狱里蹲三年。然而一个偶然的机会，唐尼在报纸上得知自己的儿子汉如今已经事业有成并大婚在即，为了避免牢狱之苦，他决定重新修复与儿子的关系以寻求资助。然而不请自来的父亲并没有得到儿子的欢迎，两人之间发生的一系列激烈碰撞不仅将汉一家搅得鸡犬不宁，还顺带把婚事也搞黄了……
Opening in the year 1984, 15-year-old outgoing and rebellious wild child Donny Berger brags to his friends about scoring tickets to Van Halen. One of the friends suggests taking a girl who they think is cute, but Donny declares he's not into girls anymore...he's into women. Ms. McGarricle (Eva Amurri), the sensually hot teacher is seen walking through the halls of the school, attracting the attention of many young boys. Donny makes a very stupid move trying to hit on her by inviting her to the concert and asking for a handjob, resulting in a month's worth of detention by Ms. McGarricle.
In detention, however, Ms. McGarricle comes on to Donny, a very obviously inexperienced virgin, and invites him into her office, where his friend can hear the action. We see that this affair continues over several occasions, culminating during a school assembly, where they are caught having sex behind the stage curtain. As Ms. McGarricle runs away embarrassed, the entire student body (and a few faculty members) begin applauding Donny, then give him a standing ovation as he runs upfront and embraces his victory.
Ms. McGarricle is put on trial for statutory rape (having sex with a minor), where the judge sentences her to 30 years in jail because the affair has resulted in a pregnancy. Donny's dad is pissed because the baby will be in his custody. As a result of this scandal, Donny becomes a nationwide sensation, getting a deal for a TV movie and becoming an overall celebrity.
Present Day. Donny (Adam Sandler) meets with a man named Jim Nance (Rex Ryan) who informs Donny that he owes the IRS $43,000 after skipping taxes since 1994. They both talk about Donny's son whom he hasn't seen since he moved out, evidently because he was named Han Solo and was incredibly overweight. Jim suggests Donny get him to help, but he doesn't think that'll do anything. Jim also tells Donny about an obese man running in a marathon, and the odds on him are 8,000 to 1. Donny then bets $20 on him.
Donny goes to a strip club and talks to waitress Brie (Ciara) and stripper Champale (Luenell). He sees a magazine with his son's picture, now very slim and having changed his name to Todd Peterson, and even making up a story that his parents died in an explosion. Donny learns that his son is getting married and that he is a successful hedge fund manager.
In the next scene, we are introduced to Todd (Andy Samberg) and his fiancée Jamie (Leighton Meester). He is so nervous about her overbearing and annoying parents coming over that he even has a spare pair of underpants with him. She tells him to relax.
Meanwhile, Donny goes to see a guy named Randall Morgan (Dan Patrick) for money. He bumps into Vanilla Ice (playing himself), who hates Donny for sleeping with his mom. They get into a fight until Randall breaks it up. He meets with Donny privately and tells him that he is no longer relevant like he was when he was a kid, so Donny schemes to get his name back out there while scoring some money. Randall tells him to get his son to come with them to the prison where his mother is for a reunion special, and Donny will get $50,000.
Todd takes Jamie and her family to stay at his boss, Steve Spirou's (Tony Orlando), house. Jamie's brother Chad (Milo Ventimiglia), a marine, comes in and intimidates Todd. As they are having lunch, Donny appears and freaks Todd out. He pretends Donny is his old friend, giving Donny the opportunity to come up with an outrageous story about how he saved his life, which the family seems to believe. Todd pulls Donny into a room to talk to him about how he was an awful father and he needs to go away so he won't ruin his wedding, but Donny asks Todd to give him a chance, as well as going to see his mother in prison, making up a story about how she is terminally ill. Todd tells him to wear a tie for a cocktail party that's about to happen.
