I refuse to testify how hilarious Pineapple Express often can be, on the grounds that it may tend to incriminate me.

Well, not me but everyone I've witnessed smoking copious amounts of hi-grade marijuana at rock concerts, family reunions and piano recitals. Those folks will think Pineapple Express is a documentary.

Seth Rogen's reefer madness movie doesn't open until Aug. 8. Columbia Pictures provided an early screening last night, probably expecting short-term memories to lapse so people who attended will buy tickets later.

Even if you've never partaken of heathen weed, Pineapple Express can provide a contact high. Rogen plays Dale Denton, a usually-stoned process server who dates a high school student and witnesses a murder committed by a police officer (Rosie Perez) and a drug dealer (Gary Cole). Frightened for his life, Dale seeks pot, protection and munchies from his cannabis contact, Saul Silver (scary funny James Franco). Things get messy, with a third wheel (Danny McBride, The Foot Fist Way). breaking out big guns and bad attitude.

Pineapple Express -- the title refers to a potent strain of Hawaiian pot -- is basically Cheech & Chong & Brad Pitt's True Romance character meet Lethal Weapon, oh, let's say 3. It's entirely based on shock comedy, from explicit language to ears being shot off. It gets a bit tiring in the second half; the stream-of-consciousness humor goes from stoned inspiration to those mumbles just before someone nods off.

But you can count on its core audience embracing Pineapple Express, and imitating its crudest gags, like constructing a crucifix-shaped joint, or hitchhiking with one's thumb suggestively protruding from a pants zipper, or... hey, man, does that popcorn have butter on it?