Seth Rogen and Rose Byrne play a couple with a newborn baby. One day, a fraternity moves in next door. They're worried that the frat parties will go late into the night and wake up their baby. So they go next door to introduce themselves. To help cement the friendship, they bring some pot with them (cause it's a Seth Rogen movie). They get along at first, even going to a party at the frat house and having a great time (strangely, the baby doesn't wake up), but one night the frat house is partying late into the night. They call the cops on the frat, and now they're enemies.
There are a couple things going on with this movie. On the surface, it's just a bunch of dick jokes and frat boy humor. The neighbors start playing more and more elaborate pranks on each other - the funniest one involves the airbag from Rogen's car, which you probably saw in the trailer. But besides the jokes, the movie is also exploring what it's like to be in your 30s and responsible. The couple is only a few years removed from the college / party lifestyle, and you can tell how badly they want to fit in with these kids. But they also have a house and a kid, and are making the adjustment to responsible adult.
The problem is the movie doesn't explore this theme very well, and the jokes aren't that funny. Some are, but I spent way too much time in this movie not laughing. Zac Efron and Dave Franco play the leaders of the fraternity, and they aren't funny. There are several scenes of them together that feel improvised. The interesting thing about improvisation is that you sometimes have to try a lot of stuff that doesn't work before you find the stuff that does work.
A great example of this can be found on the DVD extras for The Break Up. There are outtakes of Vince Vaughn and Jon Favreau improvising a scene together, and it's interesting to watch their process. Most of what they say to each other isn't funny, but they keep working it until they come up with some funny stuff.
A good movie edits out the stuff that doesn't work. This movie leaves it in. There's a scene where Efron and Franco make up after a fight, and for several minutes they riff on "Bros before hoes." It goes on forever and isn't funny.
So, this is a misfire from Seth Rogen. It's too bad because this looked really funny, and it sounds like a funny concept. But all the funny parts were in the trailers and the movie kind of bored me.