Plot

While in his teens, Donny fathered a son, Todd, and raised him as a single parent until Todd's 18th birthday. Now Donny resurfaces just before Todd's wedding after years apart, sending the groom-to-be's world crashing down.

While still in his teens, Donny (Adam Sandler) fathered son Todd (Andy Samberg) and raised him alone until Todd's 18th birthday. Now, after years apart, Donny suddenly shows up uninvited on the eve of Todd's wedding. Donny tries desperately to reconnect with Todd and is forced to deal with the results of his bad parenting skills.—Official site

In 1984, 13-year-old Donny Berger begins a sexual relationship with his teacher, Mary McGarricle (Eva Amurri Martino). When the two are discovered engaging in sexual activity on a piano during an assembly, she is sentenced to a lengthy prison term and it is revealed she is pregnant. Donny's abusive father is granted custody of the child, whom Donny names Han Solo Berger, until Donny turns 18. For a brief period Donny is a media sensation & a teenage idol, appearing on talk shows & magazines.

In 2012, Donny (Adam Sandler) is a broke alcoholic slacker who spends his time with his friends, bartender Brie (Ciara) and stripper Champale (Luenell). Donny is estranged from his son who, embarrassed by Donny's immaturity, has changed his name to Todd Peterson (Andy Samberg). Todd, a successful businessman, has recently arrived at the Cape Cod house of his boss, where he is to marry his fiance, Jamie Martin (Leighton Meester). Jami's brother Chad is a tough ass military man has joined them for the wedding.

Donny learns from his lawyer, Jim Nance (Rex Ryan), that he owes $43,000 to the IRS in back-taxes and will be imprisoned for three years if he doesn't repay the money by the end of the weekend. He visits TV producer Randall Morgan (Dan Patrick), who had produced shows for Donny during his brief period of celebrity, and Morgan offers him $50,000 if he can organize a reunion with Todd and Mary McGarricle at the women's prison.

Donny arrives at Cape Cod to try to convince Todd to participate. Because he had previously told people that his parents had died, Todd introduces Donny as an old friend. Donny elaborates with a heroic backstory and, despite his extremely crude demeanor, quickly becomes well-liked by the others, at the expense of Todd's popularity. Donny tries to convince Todd to come to the women's prison to see his mother, without revealing that it is for a TV show by saying that Mary is very sick & undergoing surgery & Saturday is the last visiting day before the surgery, but he refuses. Todd fights constantly with Donny about his father's immaturity, both now and during his childhood. Donny admits he was wrong for his actions and should've stopped himself. However, he says he didn't know how to be a father because his own father didn't teach him how to be one.

After spending more time with Donny, Todd soon imitates his father's behavior, ultimately having the wedding rehearsal at the church canceled by engaging in a fist fight with Father McNally (James Caan), the parish priest (McNally confronts Todd when Todd says that his father wasn't a good father, so he doesn't miss him anymore. Todd decides to stand up for himself when McNally asks him to apologize, which leads to the fistfight), who begins to speak in an obscure language after being hit by Todd during the incident. Donny saves him from further embarrassment by convincing the in-laws to move the wedding rehearsal to a different location because Todd is still recovering from the explosion in a church that his parents died in when he was young.

Donny joins Todd and his friends at Todd's bachelor party, a relaxing day at a spa. However, Donny offends the employees and guests and eventually convinces the guys to attend a strip club where Todd bonds with Brie. The group gets drunk and high and commits various acts of debauchery. Over the course of the evening, Todd bonds with his father and agrees to meet his mother (Susan Sarandon) at the prison. Donny, knowing that a TV crew will be waiting, tries to stop the meeting from happening, but Todd goes to the prison anyway. Todd, Donny, and Mary are ambushed by the film crew and a disgusted Todd leaves without signing a release form, leaving Donny without any money.

Donny overhears Jamie on the phone with Todd's boss, Steve Spirou, having a conversation that implies they've been sleeping together behind Todd's back. He tries to warn Todd, but Jamie comes up with a convincing cover story. Later, Donny discovers Jamie having sex with her younger brother Chad (Milo Ventimiglia) at a hotel room. Realizing that she could lose Todd if Donny tells him about her sexual affair with both Chad and Steve, she gives him a $50,000 check in order to keep him quiet.

After receiving a best man's present from Todd, an oven mitt he used to cheer him up when he was younger, Donny decides that in spite of Jamie's hush money, he has to stop the wedding. He teams up with his friend from his brief celebrity days, Vanilla Ice, in a desperate bid to get to the wedding in time. At the ceremony, he reveals himself to be Todd's father and rips up Jamie's check. He forces her to admit her infidelity to Todd. Jamie reluctantly does confess by whispering in his ear about her sexual relationships with both his boss and Chad. A disgusted Todd breaks up with Jamie and calls off the wedding. He then tells his boss that he quits his job, acknowledging Donny as his father and even taking back his birth name of Han Solo Berger.

The following day at the strip club, Han reveals that he is dating Brie and offers Donny the money to help pay for the unpaid taxes. However, Donny refuses Han's offer, stating that it's time for him to grow up and accept responsibility for his own actions. Donny is preparing to go to prison and rekindle his relationship with Mary, when a bet he placed wins him enough money to satisfy the IRS. The film ends with Donny and Han celebrating with the rest of their friends.