Surprisingly a lot, actually. Slate recently posted a video essay that reveals the peculiar and perfect connections between two sub-genres of films that couldn't seem to be less related: film noir and stoner comedies. If you're a complete film theory/history nerd like yours truly, you're going to want to learn all about "Slacker Noir".
Now, it's important to know about each of these sub-genres to really get a handle on what the video is talking about. First, film noir. So much study has been done on this type of film, specifically by French critics Etienne Chaumeton and Raymond Borde, who characterized these stark, black and white melodramas as "oneiric, strange, erotic, ambivalent, and cruel." Though these five attributes don't completely define or even relate to every film noir, they do speak to the lion's share of them, like The Maltese Falcon, The Big Sleep, Double Indemnity, and Mildred Pierce .
Stoner comedies, however, don't really have decades of scholarly articles and books written about them, dissecting the narrative and cinematic style. However, I think most of us can agree that these films feature a protagonist that is obsessed with searching or escaping from something or someone. (99.99% of the time the search involves weed; 99.99% he/she is escaping from a drug dealer -- or the fuzz -- or aliens or something.)
The video does a fantastic job of connecting the dots between the two sub-genres, however, I couldn't help but wonder, "Why stoner comedies?" There are so many other genres of films that could potentially relate (and do) to film noir, but of all of them -- stories about slackers, stoners, and the innocent pursuit of something so stupid and simple.
And then -- aha! That's it. Innocence. After doing a little digging, I found that Slate actually wrote a piece back in 2007 about why stoner comedies appeal to audiences, and in it, something profound jumped out at me:
Besides the act of looking for marijuana, the other main activity in a stoner movie is escaping authority figures (often the police, but occasionally campus security guards, co-workers, or parents) who don't just oppose the stoner's flagrant drug usage but their lifestyle of leisure and innocence.
"Their lifestyle of leisure and innocence." That's why stoner comedies work so well as noirs. Film noir is all about fractured innocence, high stakes, life or death -- the opposite of leisurely taking rips with your friends down in your basement. Putting a stoner character in the middle of the film noir universe is really very brilliant, because he/she is a direct contradiction to the highly capable, though highly unvirtuous private eyes, cops, and detectives driven solely by the desire to solve the crime (or save their own necks).
The stoners in these comedies, like the video explains, just want to go home, man. They're plopped into a world full of sin and greed, and they're relatively unblemished and pure. They just want to go back to their comfy, mellow lives with their friends and forget that all of the heavy stuff. However, in the end, it's usually this innocence that leads them to overcoming their obstacles, allowing them return to the world they never wanted to leave.