Forgive the phrasing, but the stoner comedy Pineapple Express starts on a high note. It’s 1937, on a military base filmed in black and white. (Stay with me: The prologue will make you wonder if you’re in the wrong theater even if you’re not baked.) The government is testing “Item 9” on one Pvt. Miller (Bill Hader), who’s forced to smoke the substance in a sealed room. “How do you feel?” a researcher asks. “Well, sir, I feel like a slab of butter melting over…a big ol’ pile of flapjacks,” Miller says—extremely slowly. A follow-up about what Miller thinks of his boss induces a series of random impressions of musical instruments, assurances that “This [stuff] is great,” and then a string of expletives. The government’s conclusion is vehement and swift: “Illegal!”

Cut to the present, and Dale Denton (Seth Rogen) is toking and driving, also apparently demonstrating how harmless marijuana is by calling in to a talk show to argue for decriminalization. Dale makes his living as a process server, meaning he needs to come up with clever ways to deliver subpoenas and gets sworn at a lot. To make life more pleasant, he smokes—constantly—and has recently begun buying from Saul (James Franco), the quintessential dealer: a genial longhair who’s on the couch nearly 24/7, watching old sitcoms and dozing with snacks close by. Saul is a puppy and takes a liking to Dale, selling him the new, rare strain of weed that gives the film its name and trying to get him to hang around by saying they can “look at some crazy things on the Internet together.”

The rapport between Rogen and Franco is immediately charming, and the movie’s best scenes are the early ones establishing their characters. Dale is typical Rogen, schlubby and stunted—he’s dating an 18-year-old high-school girl—but with hints of levelheaded promise. And Franco, a former member of the Judd Apatow family (Freaks and Geeks), has made up for years of forgettable, wooden dramatic turns with Saul: He’s more sweet than smart, loyal to his friends, and deals so he can take care of his grandma. Saul’s surfer-dude demeanor may scream stereotype, but Franco’s eyes have a sparkle beneath their glaze that’s irresistible.

More important, it’s pretty funny when they’re high together. Rogen and longtime friend/Superbad co-writer Evan Goldberg clearly write what they know: Watching the characters cough may get old fast, but odd stoner habits (what is it about ancient TV shows?) and conversations steered by short-term memory loss and sudden flares of hypersensitivity are more entertainingly subtle than the whoa-dude caricatures of Cheech & Chong and even Harold & Kumar.

But then Pineapple Express turns into an action movie, which is weird for a couple of reasons, not least of which is that the director is David Gordon Green, who made Snow Angels and All the Real Girls. Though the remainder of Pineapple Express’ 113 minutes isn’t exactly a comedown, the film starts to feel like it’s desperately chasing that first buzz. Dale and Saul’s imbroglio begins when Dale is sitting in his car outside of the home of Ted Jones (Gary Cole), smoking while waiting to serve the guy papers. Dale freaks out when a cop (Rosie Perez) pulls up behind him; when she goes into Ted’s house and they both shoot a third man in plain view, Dale freaks some more. He tosses his roach, spectacularly un-parallel parks, and runs to his only sorta-buddy for guidance. (The script is also sharp at addressing the unusual faux friendship that usually develops between a dealer and his clients.) When Saul tells him that he bought his stash of express indirectly from Ted—and that Dale’s the only person he’s sold it to—they hightail it, certain that Ted will find the joint and know that one of them witnessed the killing.

After a tedious scene of the pair hiding in the woods, the movie is overtaken by lots of hysteria and violence, countered only by interludes of now-familiar Apatowian bromance. Saul, Dale, and Saul’s supplier, Red (Danny McBride), bond, fight, and make up more realistically than anything starring Sandra Bullock; meanwhile, Dale’s relationship with his girlfriend (Amber Heard) exists only to show how immature he is. The later scenes are fitfully amusing, but mostly just brash, if not downright surprising: Dale and Saul’s half-assed attempts at hand-to-hand combat are usually funny, but at some point the filmmakers go all Bad Boys on us, with machine guns wielded and people actually dying. In one scene, it seems as if Rogen, after Dale pile-drives Red into a wall, asks, “Was that too much?” as himself, not his character. Yeah, it’s a little too much. But you’ll get that flapjack-butter feeling all over again when the guys later recap their adventure as if it were a crazy frat party—or a different movie.