It's easy to see why generations of stoners have embraced cinema: Movie theaters sell munchies galore, require nothing but sitting still, and offer countless options for the easily entertained (a former roommate, who shall remain nameless, unironically told me that a stoned screening of 2009's Cloudy With a Chance of Meatballs was one of the greatest experiences of his life). And obviously, for marijuana aficionados, the appeal of a stoner comedy is watching it stoned. It's A Very Harold & Kumar 3D Christmas is openly hawking this appeal; in a recent interview with The A.V. Club, John Cho suggests that viewers, "Drink what [they] want, smoke what [they] want," before going to see it.

But even sober, there's an appealing loopiness to the stoner comedy: a genuine sense, increasingly rare in cinema, that anything can happen. Even failed stoner comedies tend to fail while daring greatly—by, say, including a superfluous, incomprehensible five-minute musical interlude in which the main character hallucinates a meeting with Sasquatch. In 2004, when America's top-grossing comedy was a stunningly bland sequel to Meet the Parents, Harold & Kumar Go to White Castle offered a scene in which its two lead characters smoke marijuana with a cheetah before mounting it and galloping off into the forest. It's a Very Harold & Kumar 3D Christmas carries on the franchise's proud legacy of anything-goes comedy: Harold shoots Santa Claus, Neil Patrick Harris meets a hard-partying Jesus Christ, and the film briefly segues into Rankin/Bass-esque claymation. And that's just in the film's trailer.

While they may not have the obvious social heft of the somber documentaries and self-serious Citizen Kanes of the world, there's a brilliantly subversive streak to the stoner comedy. Look at Harold & Kumar: This is a successful, mainstream Hollywood franchise, playing in more than 2,000 theaters across the nation, that stars two non-white leading men. John Cho can joke about being the "best Korean-Indian stoner comedy duo in cinematic history" because there's never been a Korean-Indian duo, stoner comedy or otherwise, in cinematic history.

There have been other unprecedented heroes in the stoner genre, though. Cheech Marin—who, along with Up in Smoke costar Tommy Chong, is one of the undisputed patriarchs of 420 cinema—starred in four movies (three of them marijuana-centric) at a time when Mexican-American leading men were virtually unheard of in Hollywood. And the first entries in the early-'90s renaissance of the stoner comedy genre—Friday, Half Baked, and How High—offered leading-man roles to black actors like Ice Cube, Chris Tucker, Dave Chappelle, Method Man, and Redman. Even comically, the Harold & Kumar franchise has consistently confronted contemporary racial issues; in White Castle, both men are antagonized and arrested by a racist police officer, and they're sent to Guantanamo Bay in the film's sequel after a fellow airplane passenger turns them in as terrorists.

But the stoner comedy genre has done more than broaden the racial dynamics of Hollywood; it's also reflected a shift in public opinion toward marijuana itself. The stoner comedy renaissance of the '90s was accompanied by a dramatic uptick in support for marijuana legalization. That change has continued to the present day; a Gallup poll released last week revealed that for the first time in American history, a majority Americans support the legalization of marijuana. The entertainment industry has rapidly (and lucratively) adjusted to this shift in public opinion: In 2008, the stoner comedy Pineapple Express made more than $100 million at the global box office, a box office take that would have been unheard even a decade early.