Mac and Kelly win the feud by tricking the frat into having a party while on probation and Teddy is arrested and he loses the frat house. Teddy gets a job as an Abercrombie & Fitch door greeter and Mac runs into him while shopping and there are no hard feelings.
Mac and Kelly (Seth Rogan and Rose Byrne) have trouble adjusting to being "boring" parents and it is Teddy's (Zac Effron) dream to throw the most legendary party with his fraternity. Mac and Kelly make a deal with Teddy when the frat first moves next door to them that the frat will keep it down if they call Teddy first and not the police. The deal gets broken and the police tell Mac and Kelly not to call them again so the prank war begins. Mac and Kelly try various schemes to get the frat to move and succeed in getting them put on probation. After this, Mac and Kelly send a fake letter to them saying their probation is over so Teddy throws the legendary party he had dreamed about. The police come and Teddy takes the rap for his frat brothers and they lost their house. The film ends with Mac and Kelly enjoying being happy parents, and Teddy working at Abercrombie & Fitch as a shirtless door greeter. Mac sees Teddy and they talk normally and it appears there are no hard feelings.
Thanks Amanda S!