I shouldn’t be surprised. Seth Rogen and his longtime writing partner Evan Goldberg cooked this up, along with Jared Stern, and coherency is not their strong suit. (See The Green Hornet.) The fact that they set up a premise and then don’t take it seriously, or establish traits in Ben Stiller’s character that he contradicts a few scenes later is par for the course.
Stiller plays an uptight Costco manager who is shocked to learn that one of his employees has been murdered in a highly mysterious manner. The local cops are idiots and don’t see any cause for alarm, but Stiller decides to form a neighborhood watch. Unfortunately, the three guys who show up for the initial meeting (Vince Vaughn, Jonah Hill, Richard Ayoade) seem more interested in carousing than crime-fighting. Then these bunglers discover that they’re not hunting an ordinary criminal at all: they’ve stumbled onto an alien invasion right in their back yard. Supposed hilarity ensues.
But as we all know, comedy is a personal matter. If you enjoy this brand of humor, you’ll probably have a better time than I did. Just hide the bag of pork rinds under your jacket.