The premise of “Hot Tub Time Machine” is mostly contained in its title, so you pretty much know what you’re getting, sight on scene. Actually, even if you fell down some stairs and woke up at the beginning of the movie, there still wouldn’t be much room for confusion; the film’s pre-title sequence is a moving collage of historical jacuzzi scenes set to ‘80s music.

So it’s a hot tub that’s a time machine. To the 1980s. Not quite all the way there with the title, but then I guess “Hot Tub Time Machine: Freedom of ‘86” might have been pushing the limits just a tad. Either way, there you have it. It’s one part “Ski School,” two parts “Groundhog Day,” and fill in the rest with “The Hangover.”

Sorry, what’s that? You want that title one more time – slowly? Here we go.

Hot tub: It’s a scatological sex romp – juvenile as all heck. Most of that comes with Craig Robinson’s cuckolded sad-sack, Nick, and Rob Corddry’s cripplingly depressed party animal, Lou. Nick’s first scene ends in wet dog poop; Lou explains the proper degree of erection for oral sex. Lou’s ambiguously suicidal character introduction might be the funniest scene in the movie, and Corddry keeps it coming with the sharp tongue and shriveled black heart of a professional insult comic. The humor is gross, sexist and homophobic, but it’s all silly enough to forgive.

Time machine: It’s over-the-top and absurd, with much higher priority placed on fast-paced comedic impact than on smooth plotting or character development. Not that there isn’t any character development, or even a solid story-driven message – John Cusack’s heartfelt Adam discovers firsthand the wondrous unpredictability of the universe when he meets Lizzy Caplan’s vapidly whimsical music journalist April (what critic Nathin Rabin would call a “Manic Pixie Dream Girl”) – just that none of that high concept stuff matters to your enjoyment of the film. The humor hits hard and fast, no matter how little any of it means.

Freedom of ‘86 (sticking with this): It’s an ‘80s-reference jubilee for which you need only have seen VH1’s “I Love the ‘80s!” to get every last reference. Like right after John Cusack’s Adam has just done what John Cusack does best – get dumped – and he consoles himself with Peter Gabriel’s “In Your Eyes.” This movie will never let you forget what decade it is. The jheri curls are thick and bouncy, the Day Glo is dizzying, and also there’s Chevy Chase.

Which brings us to the film’s obsession with its own influences. Besides ‘80s comedy legend Chase, there is Crispin Glover of “Back to the Future” (who actually gets one of the movie’s funniest running gags) as well as 1980s Hollywood’s go-to stuffy twerp, Billy Zabka. The control panel on the hot tub has the same read-out as Doc Brown’s DeLorean, a coked-out Nick tries to explain the time travel in “Terminator,” Lou uses the Biff Tannen sports almanac trick, and so on. Even recent comedic cousins like “Wild Hogs” get name-dropped. See this movie only if you can stand near-constant pop-culture bombardment – and chances are you can, especially if you are a college student.

Put all that together, toss in the mostly expendable Clark Duke as Adam’s nerdy nephew Jacob (so forgettable that he literally flickers in and out of existence) and “Hot Tub Time Machine” is a full-grown man-child of a buddy comedy, in the recent tradition of Apatow’s “Frat Pack.” It may be really, really dumb, but it’s funny enough. The agile on-screen chemistry engages pretty consistently, the bro-mances triumph over the romances, and there’s plenty of lady breast and dude butt to go around.

Garth Brody can be reached at [email protected].