Mac (Seth Rogen) and Kelly (Rose Byrne) Radner try to have “spontaneous” sex in their dining room. Their six-month-old daughter Stella (Elise and Zoey Vargas) won’t stop watching them, so they give up. Having a baby and owning a house doesn’t make them old, they declare. When Mac leaves for work, he and Kelly see a biracial gay couple with an infant taking a tour of the house next door. This is the second dream scenario (the first being, according to Mac, a Taco Bell opening up next door).
At work, Mac’s boss Bill (Brian Huskey) tells him he needs a file by the end of the day. Mac’s friend Jimmy (Ike Barinholtz) interrupts them, claiming he and Mac have another important file to work on together. It proves to be an excuse for the two of them to sneak out back and smoke a joint. Jimmy asks about Stella and Kelly, and Mac admits their lives have mostly returned to normal. Kelly won’t let him see her breasts anymore, opting to wear a wife beater during sex, but he can deal. Jimmy says that because Mac and Kelly are the only people in their friend group to have a kid and a house, it makes them seem a decade older than the rest of them. Jimmy, who is recently divorced, describes how sexually free women have become. Mac looks worried that he has become boring.
That night, Jimmy’s ex-wife Paula (Carla Gallo) calls Kelly and Mac, begging them to come out with her. They don’t have a babysitter, so Paula suggests they bring her along with them. Mac and Kelly are desperate enough to get out that they agree. When it comes time to pack all of the things Stella will need, they become so overwhelmed that they collapse in their doorway. At the end of the night, Paula calls them to brag about what a fabulous time she had. Kelly is distraught.
A few days later, Delta Psi, a fraternity, moves in next door. They observe their new neighbors from their porch. “That is the hottest guy I have ever seen,” Mac says about Teddy (Zac Efron). “He looks like something a gay guy designed in a laboratory.” They quickly realize that the fraternity will throw lots of loud parties. Kelly and Mac agree they need to introduce themselves to the brothers and tell them to “keep it down.” To emphasize their coolness, they will also offer them some weed. They receive a warm greeting from the men of Delta Psi. Teddy and Pete (Dave Franco) are in charge and fawn over Stella. Teddy even flirts with Kelly. Mac offers them a joint, and the brothers cheer. Kelly kills the mood when she yells, “Keep it down!” Teddy agrees they won’t make too much noise and asks them to check in with him or Pete before calling the cops.
Teddy and Pete address their brothers in the basement of their new home. According to them, Delta Psi has a rich history of epic party moments. In the 1930s, the frat created toga parties. In the 1970s, they invented beer pong. Teddy and Pete want to add their faces to the fraternity’s Hall of Fame by throwing the most outrageous end-of-the-year party ever. They end the meeting by chanting loudly. The noise wakes Mac and Kelly. They hear loud music, too and go next door to ask the guys to turn down the volume. Teddy answers the door, revealing a drug-and-booze fueled party. He agrees to turn the music down. Mac and Kelly are intrigued by the party, but Teddy says good night to them. Upon further reflection, Teddy tells Pete they should invite “the old people” to their party. They want to get on their good side, right? He and Pete open the door and call after Mac and Kelly. Kelly has a baby monitor on her phone, so what’s the harm in coming inside for a tour of the house? Mac and Kelly, desperate for excitement, go inside the fraternity.
Mac does drugs with Teddy and Pete. Kelly dances with college girls. Eventually Teddy brings Mac to his room, the Lion’s Den, which encompasses the entire top floor of the house. The Lion’s Den is off limits during parties, and it’s where the guys keep their most important belongings: drugs, passports, extra ping pong paddles. Mac notices a huge stash of fireworks in the corner, but Teddy tells him the last time Delta Psi used those, they burnt down their house. He ends the tour by showing Mac the breaker box. Flipping one of the switches turns on all of the neon lights in the backyard. “Welcome to paradise,” Teddy says to Mac. Mac and Kelly spend the rest of the night bonding with Teddy and his girlfriend Brooke (Halston Sage) respectively. When they go home in the morning, Teddy asks if they were serious about Delta Psi keeping the noise down. Kelly and Mac say they were. Teddy reminds them to call him before calling the cops if the fraternity is too loud.
Another night, another Delta Psi party. Mac calls Teddy ten times to tell him to quiet down, but no one answers the phone. Kelly tells him to call the cops anonymously, so the fraternity won’t know they made a complaint. They watch a police car pull up next door. Teddy and Pete come outside to talk to Officer Watkins (Hannibal Buress). Kelly and Mac panic when Watkins points to their house and all three men come to their door. At first Mac pretends he didn’t call the police, but Watkins reminds him of caller ID. When Mac and Kelly complain about the noise, Teddy protests that they were partying with them last night. He shows the cop a drunken video of Mac. Mac rescinds the complaint, and Watkins accuses him of crying wolf. “Never call us again,” he warns. Teddy feels betrayed by Mac and Kelly. “I’m not mad,” he tells them, “I’m just disappointed.”
The next morning Mac and Kelly awaken to find their lawn strewn with toilet paper and empty beer cans. Later, Pete cuts one of their “expensive bushes” into the shape of a bent over man. When Mac and Kelly try to remove the bush, it looks as though they are having sex with it. Mac thinks they should lead a neighborhood-wide revolution against Delta Psi’s antics, but they find that the fraternity has befriended everyone living in the surrounding houses. Their realtor says they cannot sell their house, because no one wants to live next to a fraternity. The next afternoon, Mac and Kelly clean their front lawn of Delta Psi debris. They leave Stella on a blanket and are horrified when they discover a condom in her mouth. They rush her to the emergency room, and thankfully, she is fine. Mac and Kelly go to Dean Gladstone (Lisa Kudrow) at Delta Psi’s university, but she cannot help them either. The university has a three strikes policy when it comes to fraternities, and burning down their previous house only counts as their first strike.
Back at their home, Mac and Kelly have reached a tipping point. Kelly proclaims that she is a mama bear who must protect her cub. They decide to cause damage to the fraternity’s house, because Delta Psi does not have enough money to cover monumental repairs. They could force them to move. Mac busts their pipes, causing the basement to flood. The brothers gather to assess the damage, and Pete tells them the foundation of the house is ruined. Scoonie (Christopher Mintze-Plasse) complains that they need to take action, not stand around with “their dicks in their hands.” This gives Teddy and Pete the idea to create and sell Delta Psi dildos to raise the money they need. Their sale is successful enough that they cannot only fix their basement but also purchase a gigantic hot tub and outdoor speakers. Their parties become louder and rowdier.
Kelly comes up with a plan. Fraternities are founded upon brotherhood and loyalty, so they need to get someone from Delta Psi to put “hos” before “bros.” Mac doubts such a feat can be accomplished, but Kelly has noticed the way Brooke looks at Pete. She suspects Teddy’s girlfriend and his best friend have a thing for each other. She enlists Paula and Jimmy to help them. Mac and Kelly hire a babysitter for Stella, and they take their friends to a Delta Psi party. Mac tells Teddy he wants to broker a truce, and the pair engages in a friendly dance-off. Kelly sends Paula to distract Scoonie and Jimmy to distract Brooke’s best friend Whitney (Ali Cobrin) so she can push Pete and Brooke together without interruption. When Brooke and Pete inevitably head upstairs to have sex, it is Mac’s responsibility to point Teddy in their direction.
Everything goes according to plan. Kelly finds Brooke and Pete and jokes about the two of them hooking up. She kisses Brooke seductively and then kisses Pete. To seal the deal, she pushes Brooke and Pete together. After a moment’s resistance, they make out wildly and quickly head upstairs. Mac swivels on the dance floor so Teddy sees them holding hands. He goes searching for them. Moments later, Garf (Jerrod Carmichael) bursts into Pete’s room, where he is having sex with Brooke. He tells them that Teddy saw them. Pete finds Teddy, but when he asks if he’s okay, Teddy punches him. They grab each others’ balls, and Pete uses his secret skill of becoming erect at will to get Teddy to let him go. Mac cheers that they should throw things off of the porch, and Teddy is upset enough that he agrees. When he throws a lit barbecue off of the porch, it rolls into the path of an oncoming car. The barbecue bounces off of the car and hits an old man walking down the street. The man lives, so Kelly and Mac feel victorious. They get incredibly drunk to celebrate.
The next morning they wake up to peace and quiet. Kelly’s breasts are painfully full of milk, but she cannot nurse Stella because she is still a little drunk. She lifts her top to reveal darkened veins snaking away from her nipples. “Your boobs look like my grandma’s legs,” Mac complains. To his dismay, he has to milk his wife. When Kelly feels more comfortable, they agree that it was worth it, because Delta Psi will disband.
Teddy, Scoonie, and Garf sit in Dean Gladstone’s office. Teddy wants to know where Pete is, and Scoonie tells him he is at the jobs fair. When Dean Gladstone arrives, she berates them for injuring the man on the street. This is their second strike, and they are on probation for the rest of the school year. If they throw any kind of party, she will shut Delta Psi down. Afterwards, Teddy finds Pete at the jobs fair. They make amends, and Pete returns to talking to prospective employers. Teddy speaks briefly with someone at AT&T’s booth, but given that he doesn’t know what the company does, he is turned away.
Kelly and Mac go to Jimmy to get him to help them give Delta Psi their final strike. They say they dislike how messy the fraternity is, but Jimmy thinks they want to party with the brothers again (rather than go back to their boring lives). Kelly and Mac goad Jimmy into helping him by reminding him that Paula is hooking up with Scoonie (who happens to have a giant penis). Jimmy buckles and asks them, “What’s the plan?” Mac knows hazing gets fraternities in lots of trouble. They invite on of Delta Psi’s pledges, Assjuice (Craig Roberts), out for coffee to get him to spy on Teddy and the others. They remind Assjuice of how poorly Teddy, Pete, Garf, and the others treat him. Assjuice flashes back to some of the indignities he has suffered: being teabagged, being hit, being scared out of bed by a deer head so he jumps into a pile of poop. Assjuice tells Kelly, Mac, and Jimmy he has endured hell and has been promised infinite blowjobs once he becomes a full-fledged brother. He won’t turn against Delta Psi. Then Kelly offers him $1000, and he buckles.
Jimmy gives Assjuice a pair of glasses with a camera built into the frame. It will record everything Assjuice sees. Mac, Kelly, and Jimmy watch from a computer as Assjuice and the other pledges are forced to crawl around naked, in a circle, with their noses pressed to the next pledge’s butt. Teddy, Pete, and the others scream insults at them. Assjuice breaks ranks and bellows that he’s a human being. Teddy seems furious. “I’m going to haze you so hard your face falls off,” he yells as Kelly, Mac, and Jimmy cheer. With that footage, it seems certain Dean Gladstone will shut down Delta Psi. Teddy drags Assjuice into another room, but instead of hurting the younger man, he is concerned from him. “In my opinion,” he says, “you’re one of our strongest pledges.” He wants to know if Assjuice is alright. When the pledge admits he’s tired and stressed, Teddy sends him upstairs to rest. The trio are no longer celebrating. Their mood sours even more when Assjuice confesses to Teddy that Kelly and Mac hired him to spy on Delta Psi. He tells them that Kelly and Mac are also behind the busted water pipes and getting Pete and Brooke to have sex. Teddy takes his glasses, looks into a mirror, and tells the couple they have gone too far.
The next morning, Kelly finds that the airbags in her car have been removed. She calls Mac at work to tell him she thinks the fraternity is behind the theft. Mac sits down on his chair and is catapulted into the ceiling as one of the airbags deploys. Moments later Jimmy sits down and suffers a similar injury. When Mac returns home, Kelly tells him, “We went too far, and now it’s getting dangerous.” Mac, on the other hand, is focused on revenge. Kelly tells him to grow up, because their family might be in danger. “You should take responsibility,” Mac snipes. He thinks Kelly should have stopped him from engaging in warfare with the fraternity in the first place. Kelly is offended. She doesn’t want to have to be the responsible one all of the time and just because she’s a woman. She tells him she doesn’t think they’re a good team anymore, and Mac agrees. Kelly grabs Stella and leaves him to find the rest of the undeployed airbags (of which there should be four remaining). Pete and Teddy watch Kelly strap Stella into her carseat and drive off. Pete, as a child of divorce, worries that they have contributed to the failure of Mac’s and Kelly’s marriage. Teddy, as the child of parents who love each other, replies that he couldn’t care less.
Mac deploys the rest of the airbags and eventually ends up in Stella’s nursery. Seeing her empty crib makes him miss her and Kelly, so he drives to Paula’s house, where the pair have been staying. Kelly has missed him just as much, and they kiss and embrace.
Pete finds Teddy sitting in front of Delta Psi’s Wall of Fame. Teddy is depressed that they won’t be able to throw any more parties and that he will therefore not be able to put his picture on the wall. Pete says none of the stories about the brothers on the wall are true anyways, so he should put his picture on the wall if it means that much to him. Did he really think Delta Psi brothers invented beer pong? Teddy is incensed that Pete would doubt their lore, and Pete encourages him to think about the things that actually matter, like their lives after college. He thinks Teddy is so focused on “the old couple” because they remind him of the future, and he hates that. Teddy tells Pete to go fuck his girlfriend again. Did Pete really think Teddy would get over that so easily? The two part angrily. After Pete leaves, Teddy sees Mac and Kelly pull up in their car. They kiss on the sidewalk. He goes over to their house, but neither of them wants to see him. To Mac and Kelly, the war is over. Teddy reminds them that he will be gone in a few months, but many more will replace him. He taunts them by saying that Stella will grow up watching shirtless, handsome boys. He reignites his neighbors’ anger.
Kelly and Mac have drinks with Jimmy and plot Delta Psi’s demise. Jimmy inadvertently gives them the idea to send Teddy a fake letter from Dean Gladstone saying that Delta Psi’s probation has been revoked. When Teddy receives the letter, he is ecstatic. He and the others set to work planning the most epic party ever. Kelly, Mac, and Jimmy do different celebrity impressions so they can call into radio stations and promote the party.
The night of the party arrives. Teddy and the other brothers have hotboxed the entire house. Hundreds of guests arrive, and the party is insane. Next door, Mac calls the cops to complain about the noise. Officer Watkins responds to the call. Garf finds a flier promoting the party and brings it to Teddy. Delta Psi promotes its parties exclusively online. They realize that Mac and Kelly must have something to do with it, because only old people would use fliers to promote something. Teddy shows Garf and Pete the fake letter, and Pete notices there is Hebrew on the school’s insignia rather than Latin. They panic and shut down the party. As the music stops, the lights come back on, and people stream out of the house next door, Kelly and Mac realize Delta Psi has stopped the party. Jimmy confesses he used Hebrew instead of Latin on the insignia, so now the three of them will have to go across the street and restart the party.
Officer Watkins pulls up to the fraternity in time to see the party has broken up. Garf comes out to assure him everything is winding down. Watkins asks Garf about his name, and when Garf says his full name is Garfield, Watkins pesters him with trivia about the cartoon cat. Mac, Kelly, and Jimmy get inside and manage to get to the second floor of house. Teddy is in the Lion’s Den, though, and Jimmy throws himself off of the balcony to cause a distraction. He breaks his leg but manages to draw Teddy out of his room. Unfortunately for Kelly and Mac, his door has a combination lock, and he slams it as he runs out. Jimmy confesses that he hurt himself to distract Teddy, and the fraternity president rushes back to his bedroom. Mac figures out the combination is 4-2-0 and gets Kelly through the door just as Teddy charges up to him. Mac and Teddy fight each other as Kelly tries to open the breaker box, which is also locked. Down on the street, Garf has finally finished his conversation with Watkins, and the officer starts to drive away. Kelly sees the fireworks in the corner of the Lion’s Den, lights one, and shoots it through the open window of Watkins’ car. Watkins loses control of his car and calls for backup just as the lights go off and the loud music begins again.
Teddy and Mac have stopped fighting, but neither knows what is going on. As it turns out, Scoonie showed Paula the secret outdoor breaker box, and he restarted the party for her. Jimmy hobbles out of the house and finds them. He tells Scoonie to get away from his wife, and the fraternity brother complies. Paula is touched by Jimmy’s possessiveness over her, and the two kiss wildly. “Let’s have a baby,” Paula tells him. “A baby will solve all of our problems,” Jimmy agrees.
Outside, Teddy finds Pete and tells him to get the other brothers and run. He will take full responsibility for throwing the party and for shooting fireworks at Watkins. Pete refuses to leave Teddy behind, but Teddy would rather he focus on his bright future. “I love you,” Pete tells Teddy before gathering the other brothers and running away. Watkins arrests Teddy, hitting him in the leg with his baton.
Mac and Kelly return home, sated by their victory. As they watch Stella sleep, they admit that their lives have changed. They will be responsible for their daughter’s life until they’re “really fucking old.” Even though it’s weird to leave their youthful antics behind, both of them have found things they enjoy about adulthood. Kelly loves the smell of freshly ground coffee, and Mac wants to grow tomatoes. They fall asleep in bed eating pizza with ranch sauce.
Four months later, Mac sees Teddy working as a male model outside of an Abercrombie and Fitch store. Despite their past animosities, the two men embrace warmly. Teddy is happy at Abercrombie because he meets lots of hot women there. Pete works at a big architecture firm now, and the rest of the brothers bought a new house just off campus. Mac asks if he can join Teddy for a little bit, and when Teddy agrees, he takes off his shirt and “models” with him. Teddy tells Mac he makes the store seem more approachable. Mac goes home, where he and Kelly are making a pop culture calendar of Stella. They receive a Facetime call from Paula and Jimmy, who are at Burning Man. They decline the other couple’s invitation to join them. Instead, they decide that after dressing Stella as Jesse Pinkman from Breaking Bad, they should dress her as Don Draper from Mad Men.
You can send in your spoiler to other movies by going here.