He's already this pale and sickly when the movie STARTS.

One thing you can say for sure about “Relaxer”: There will never be a gender-swapped remake of it. The story, first juvenile and then surreal, only makes sense in the context of men’s craving for competition and willingness to spend absurd amounts of time and energy on total nonsense. That’s not to say women won’t enjoy watching the movie, just that their takeaway message will probably be an eye-rolling, “Oh, men” (which they must be used to). Men, on the other hand, will watch it and think, “OK, I can see doing that….”

Writer-director Joel Potrykus, chronicler of peculiar men in previous SXSW premieres “Buzzard” and “The Alchemist Cookbook,” returns with frequent collaborator Joshua Burge starring as Abbie, a layabout living on his brother’s couch in the summer of 1999. When we enter the picture, Abbie is near the end of a challenge issued to him by the brother, Cam (David Dastmalchian), to drink a gallon of milk within a specified length of time without getting off the couch. We infer that submitting to ridiculous challenges like this is how Abbie earns his keep in Cam’s mournfully dingy Michigan apartment, in which the entire movie takes place.

When the milk challenge ends (disgustingly), Cam has a new one for him: beat the all-time Pac-Man record, here on whichever video game console they have in the apartment (it must be an old Atari), before Y2K. That gives Abbie five months. He still can’t leave the couch, though.

If you can’t buy the premise of someone voluntarily remaining couch-bound for days at a time to win a bet, or of being on the honor system not to break the rules, then you can stop here. “Relaxer” assumes we get it and makes no effort to make it seem reasonable. There’s no discussion of Abbie potentially sneaking away to the bathroom when Cam is out of the house, not even an assertion by Abbie that he won’t. It is simply understood that Abbie WILL NOT LEAVE THE COUCH. Period. You have to respect that.

Once Cam leaves, Abbie calls a friend to bring him supplies. That friend, Dallas (Andre Hyland), is a motor-mouthed white-trash vulgarian patterned after a Danny McBride character who shows up not to help Abbie so much as to pester him. (Eager to be included in the “challenges,” Dallas challenges himself to duct-tape a two-liter bottle of soda to each of his own hands. He does this instead of giving the couch-bound Abbie something to drink.) This section of the film is funny in the familiar way of raunch-coms (it could just as easily be Seth Rogen and Michael Cera), with Abbie, gaunt-eyed and deadpan like Buster Keaton, responding wearily to Dallas’ shenanigans while continuing to play Pac-Man.

Conversations with other visitors shed more light on Abbie, a slightly soft-brained underdog who might be too innocent for this world. (He might also have supernatural powers.) The movie gets more farcical when Abbie starts trying to use his reaching implements — he has duct tape, a cup, and the poles from a tripod — to get water, first from the rain falling outside, later from a pipe in the wall. Burge’s performance through all of this (did I mention he’s in his underwear the whole time?) is comically adept and even psychologically compelling: What’s going on in his head?

There comes a point where “Relaxer” moves past farce, evolving from “implausible but possible” to flat-out fantasy. It’s one of those “Oh, it’s THAT kind of movie” moments, and you either go with it (and what comes next) or you don’t. Having seen too many movies, I’m a sucker for surprise left turns and outside-the-box thinking, and I was delighted by the third-act developments in what had already been a witty, strange comedy. I’m not sure what I saw, but I’m glad I saw it.

Crooked Marquee

B+ (1 hr., 31 min.; Not Rated, probably R for pervasive harsh profanity, some gross images.)