In comedy, there is a wide spectrum of realism. On the one end, you have films that stick to conventional plots with largely realistic people and situations, then throw in the occasional unlikely event or silly character; on the other end, you have films that will do whatever it takes for a laugh, bombarding the audience with ridiculous characters and wild divergences from the plot and bending the laws of physics to absurd, comic ends. People generally expect comedies with a social mission — like the first “Harold and Kumar Go To White Castle,” the first mainstream comedy with Asian American leads — to fall into the former category.

In an interview, the series’ writer Jon Hurwitz said, “when [co-writer] Hayden [Schlossberg] and I were growing up, we had a lot of friends who happened to be Asian … we’d always wonder why we never saw guys like them on the big screen — if you saw Asians they’d always be doing martial arts or talking in bizarre accents. So we wrote this with the idea, ‘Hey, these are our friends, and they’re just like us.’”

Generally, comedies with a stated social goal like that are self-serious and self-righteous, too busy impressing us with how enlightened they are to remember to actually make decent jokes (they also tend to feel like condescending, cinematic charity).

“Harold and Kumar,” though, went the complete opposite route — the films offer a non-stop barrage of frequently hilarious, increasingly bizarre jokes that keep the racial politics in the subtext. That approach is what makes the movies work and the latest entry, “A Very Harold and Kumar 3D Christmas,” is no exception.

The film starts with Kumar (Kal Penn) still living the life of a stoned slacker, estranged from Harold (John Cho), who has settled into his role as an investment banker and family man. Minor digression: This part of the film features a very Occupy Wall Street-like protest outside of Harold’s workplace, a pretty remarkable coincidence considering when it was filmed. Unfortunately, in what was perhaps a misguided attempt at being evenhanded, the film mocks, as well as sympathizes with, the protestors’ aims. When Kumar finds a mysterious package addressed to Harold at his doorstep, he reunites with his former BFF, only to inadvertently burn down his Christmas tree, thus setting the duo off on a journey to find a replacement.

Normally, in a review, I’d devote most of the word count to describing the plot and making a case for whether it’s a good or bad movie. But that can be done briefly — there isn’t much of a plot and it is a good film, with plenty of inventive, hilarious sequences and a surprising amount of heart (though it also suffers from the kind of sexism typical of the genre). I think the space would be better spent exploring the film’s sly (and sophisticated) racial politics.

In a nutshell, the filmmakers deliberately set out to grant Harold and Kumar “whiteness” in this film. A key moment comes early on, when Harold (still estranged from Kumar) and his new white sidekick (Thomas Lennon), try to buy a Christmas tree from two black guys (the RZA and Da’Vone McDonald) who work at the tree lot. They tell him that they just sold the last tree to “two other white guys,” referring to Kumar and his new sidekick (Amir Blumenfeld). On the surface, it seems like the writers were trying to say that, in the eyes of black people, Asian and Jewish people are the same as white, and to an extent, that is probably partly what they were trying to say (whether or not it’s true is another question entirely). But at the same time, I think they are also making a statement: Harold and Kumar have achieved “movie whiteness” (I’ll get back to this in a bit).

In fact, a major theme in the film is the malleability of racial identity. The two black Christmas tree salesmen, when alone, discuss which one of them will get to “play the angry black man” when a customer arrives. Harold and Kumar’s friends Goldstein and Rosenberg debate whether or not someone who converts from Judaism to Christianity is still “Jewish.” Neil Patrick Harris, who plays a fictionalized version of himself, asserts that his coming out as gay in public was to hide the fact that he is a ravenous (hetero)sexual predator.

On the surface, the film’s story is about Harold and Kumar going through identity shifts as well, but theirs aren’t about race or sexual orientation (there are a couple references to Harold’s in-laws being prejudiced toward Koreans, but that is presented as a toss-away joke). Over the course of the movie, Harold learns to assert his identity as a stoner and as a spouse, and Kumar — whose ex-girlfriend reveals that she is pregnant — embraces his identity as a father. And that’s where “movie whiteness” comes in. “Whiteness” in the movies isn’t about white stereotypes, it’s about the absence of being defined by race or ethnicity. And because Harold and Kumar aren’t defined by their race or ethnicity, they have achieved parity with white movie characters; they have achieved “whiteness” in this film.

And the way the filmmakers deal with all the other characters’ ethnicities reinforces this point. Every character that is coded “non-white” in the film is defined almost exclusively by their ethnicity (or sexuality). When Harold’s wife, Maria, appears in the film for the first time, Flamenco guitar music plays (she’s also in her underwear). Her Colombian family is depicted stereotypically (and her dad is played by Danny Trejo). Rosenberg and Goldstein have heavy accents and squabble over money. And the tree salesmen utter the words “angry black man.”

While in other films I might find this offensive, what’s interesting is that in “Harold and Kumar” it functions as a form of commentary, an ongoing meta joke, that wouldn’t work if there wasn’t any contrast: Hurwitz and Schlossberg have made Harold and Kumar “white” and — given the success of the franchise — America seems to have largely accepted it. Given all the birther nonsense and the legalized racial profiling, there isn’t much to feel good about in terms of race in America these days, but a successful, uncontroversial, mainstream film that ends happily (with no trace of irony) with a Korean American and Indian American guy sharing a Christmas morning joint seems to me, at least, to be a shinning ray of hope.