I don't mind when films reference other films. Sometimes a homage is nice and suitable despite being blatant, while other times they can be overbearing and annoying. Paul is somewhere in between. The references work in one respect because this is co-writer/actor Simon Pegg's take on a sci-fi movie and they don't work most of the time because they aren't funny. They are just gags without a laugh. Pegg previously co-wrote Shaun of the Dead and Hot Fuzz, both films that are more than just genre parodies and they function without one getting all of the references. Paul on the other hand might be lacking Edgar Wright's careful direction and I say this as a huge fan of Paul's skilled director, Greg Mottola (Superbad, Adventureland).
The film follows two sci-fi nerds (Simon Pegg and Nick Frost, Frost is the other co-writer) who encounter an extra-terresetrial on the run (voiced by Seth Rogen, the film also stars Kristen Wiig, Jason Bateman, and Sigourney Weaver). The actors seem to be trying their best and are really into the material, but the story is just middle-of-the-road. In other words, everyone displays good comic timing... just not good comedy. The friendship between the two main characters is quite typical. It was as if it was placed into the film just to give the story a somewhat grounded emotional spine since a majority of this movie is action sequences, sci-fi film references, and crude language (saying penis is always bound to get a laugh out of someone). The relationship just doesn't seem interesting because there are no major conflicts other then short-lived arguements that are resolved quickly. Therefore, the only thing that differentiates the main characters seems to be their weight and the length of their hair. At least when Paul shows up, things get more lively than just watching two men walk around Comic-Con.