Despite what your expectations might be, “Hot Tub Time Machine” doesn't spend a lot of effort explaining the hot tub time machine concept, which whisks three middle-aged men back to the 1980s, right after an episode with a guy in a bear suit. Who needs explanations? The '80s, if you recall, had plenty of time machines, from DeLoreans to telephone booths. A hot tub would appear to be the logical next step.

If you're looking for a carefully executed and comprehensible plot you might want to party elsewhere, but “Hot Tub Time Machine” has its share of laughs. The movie is so unconcerned with details it feels edited by someone who was completely stoned. Maybe that's the best way to view it, but either way it doesn't take a lot of concentration to get the gist: Longtime pals Adam (John Cusack), Lou (Rob Corddry) and Nick (Craig Robinson) hate their lives, especially Lou, whose accidental near suicide prompts a trip to what was once a happening ski destination, with Adam's nephew Jacob (Clark Duke) inexplicably in tow. The place has seen better days, but a mysterious hotel hot tub makes the men feel better when it transports them to 1986, where they relive one glory day while confusing people with talk of text messaging and e-mail.

Chevy Chase shows up as a handyman who cryptically warns the trio and their ward not to do anything that would upset the space-time whatchamacallit, leading the four to try in vain not to get involved with the wrong babes, etc. But one look on his face, especially the close up with his eyes going wacky, tells you how seriously to take his character and advice.

“Hot Tub Time Machine” references “Back to the Future” and “Bill and Ted's Excellent Adventure,” but it more resembles the kind of nonsensical antics Cusack cut his teeth on, like “Better Off Dead” and “One Crazy Summer.” The movie is cheapo comedy at its best and worst, which you can take as a recommendation or a warning. (R) 100 min. HHHII