The Second Version Recommends
Horror comedies are rare; most of the times horror movies turn involuntarily comic, but that's not really a praise.
There's gore, nudity (from Jessica Alba, no less!), pot and the surreal situations and dialogues associated with being high, and the subversion of a few genre tropes, most notably what I'd call the Fake Ending*.
This is a B-movie played straight from start to finish, so do not expect anyhting groundbreaking or revolutionary. The cinematic technique here is just standard, and the plot and acting... well, who cares, honestly?
* The last scene of the movie telling us that all the toil was for nothing, because the evil is still alive, or the monster's egg just hatched or Alien laid its larva inside Predator, and so forth.