hey. i write film criticism/reviews fairly regularly, and they just sort of sit around on my computer. i figured i'd post it on the internerd this time...
While there are plenty of enjoyable moments in Pineapple Express, it is most consistent in, well... its inconsistencies. It seems clear that this bumpy ride is the product of a confused piece of screen writing. This is no secret, but to understand why this has happened one has to realize that these same handicaps show their faces in the Judd Apatow crew's most defining and celebrated movies.
Yes, most of the improv-heavy movies by Apatow and his like-minded collaborators all have some of these same weird screen writing issues with pacing and story (we're talking Knocked Up, Forgetting Sarah Marshall, and Superbad). They sometimes feel oddly structured and very amateur in their frequent avoidance of the screen writing 101 trope of "upping the stakes." Chances to heighten the urgency of story-driving plot points are frequently side-stepped, dampening the forward motion of the film and making the audience wonder what they're supposed to be caring about in the long run.
Now, why has this not been such a problem until this movie? Sometimes those decisions make Apatow and company's films feels fresh, realistic, unpredictable, and interesting. Since a comedy's main goal is to be funny and develop the characters rather than plot, it's easier to get away with less satisfying resolutions and story pacing. With Pineapple Express, we no longer have a straight-up comedy on our hands, and the genre deviation is what really hurts this one.
In making the film an action-comedy hybrid, these guys should have realized that their typical decisions would feel more sloppy than quirky when applied outside their favored genre. Unlike with Hot Fuzz (a movie which has been oddly compared to Pineapple Express when it really begs contrasting), the script here is loose and underwritten. The action lacks the parody factor that held Hot Fuzz together and is often awkwardly inserted into scenes, feeling out-of-place amidst the improvisational comedy bits, many of which simply weren't that funny when compared to this crew's past output.
If the jokes had been more consistent and frequent, maybe all the other inconsistencies would have been easier to let slide, but the decision to try to make the action-adventure plot such a strong focus and then construct it so poorly made for a film difficult to digest.