The stoner movie, a beloved and beleaguered American genre, has had its highs and lows over the past few decades, reflecting pop culture's yo-yo over the appropriateness and comedic potential of a chewy buzz.

Oh, how we laughed (or didn't) at the antics of Cheech and Chong, with their giant joints. But those were simpler times, the fabled 1970s, when a talking Chihuahua was a mere hallucination and not a tout for Taco Bell.

C&C's "Up in Smoke" set the stage for the stoner as ambulatory vegetable. Sean Penn in "Fast Times at Ridgemont High," Keanu Reeves in "Bill & Ted's Excellent Adventure," Jason Mewes in "Jay & Silent Bob Strike Back" -- walking zucchini all.

Then there are the urban bluntmen: Snoop Dogg in "The Wash," Method Man in "How High." The doobage is almost a character itself. And the lost classic: "Half Baked," which was a critical and theatrical bomb but stars the genius Dave Chappelle. You can almost smell the fumes on those rental DVDs.

Yet perhaps the most curious stoner movie in recent times is "Dude, Where's My Car?" (2000), about a pair of twenty-something apparent potheads who awake to find themselves saddled with some serious short-term memory loss. But dude, where is the herb? Not to be seen, because the studio wanted the Ashton Kutcher film to come in with a PG-13 rating, which forbids portrayals of drug use, leaving the audience to wonder: Are the dudes blackout alcoholics, and if so, is that better?

Anyway, now comes the latest entrant, "Harold and Kumar Go to White Castle," opening nationwide July 30, about a couple of recent college grads who set out simply to plug the munchie hole at a burger joint but become swept up in "an epic journey of deep thoughts and deeper inhalations," as the movie blurb has it. It is rated R, so you know exactly why they are so hungry.

The movie's screenplay is by 26-year-old roommates Hayden Schlossberg and Jon Hurwitz, best friends from their high school days in Randolph, N.J. Though familiar with the business end of a bong, the filmmakers are certainly high achievers. Hurwitz, a finance major at the University of Pennsylvania, planned on becoming an investment banker. Schlossberg, a history major at University of Chicago, was going to be a lawyer. But in their senior year they sold a screenplay, and to Hollywood they moved.

"If it's a real stoner movie," Schlossberg says, "you got to go all-out and make it an R. The characters will smoke a joint, and you need to see that."

There are some twists and some risks in "Harold and Kumar" that make this film potentially interesting. The leads (John Cho and Kal Penn) are little known, and they're Korean American and Indian American. "And usually the main characters are moronic or lazy or not go-getter people," Schlossberg says. "Not real. Not real voices. But there's a huge population of college kids who get high, who are on track in life."

"Who are going to be doctors and lawyers and bankers," Hurwitz adds.

"Or who are working at jobs," says Schlossberg, "not really sure they are into it. They come home from work, they get high and think, 'What are we going to eat for dinner?' That's people's daily lives. We take that and blow it out to epic proportions."

Early reviews have been most excellent. "A blissfully silly, character-driven road movie with impressive laugh-per-minute performance specs," Michael Rechtshaffen writes in the Hollywood Reporter. "A crafty spoof on issues from racial politics to American highway monoculture that belies its cover (and marketing) as only a dumb gross-out laffer," says Variety's Robert Koehler.

Wait a second. What is that Chihuahua saying: A stoner movie with a message?

John Cho, above left, and Kal Penn in "Harold and Kumar Go to White Castle," the latest in a genre that includes "Bill & Ted's Excellent Adventure," below left, and "Jay and Silent Bob Strike Back."