Three grown men and a young adult get drunk, decide to go hot-tubbing at their ski resort… Three grown men and a young adult get drunk, decide to go hot-tubbing at their ski resort cabin and are somehow transported back in time. Comedic hijinx ensue, and somehow this ludicrous-cum-inane concept is being projected as one of the top comedy films of the year?

I don’t get it, but if “Hot Tub Time Machine” is as good as critics are saying it is from advanced screenings, I’ll go with it.

This past summer, I saw a preview screening of “The Hangover,” and I thought it was quite funny, despite its near-complete lack of a plot. I predicted it would be insanely successful, and surprise, surprise, it was. What is it about comedies with threadbare — or worse, absurd — premises that the American moviegoers are eating up these days?

The boundaries between subgenres of comedy are thinly defined at best and always arguable. For example, the upcoming “Hot Tub Time Machine” has all the ingredients of a stoner comedy: a premise that might make sense only when under the influence, stupid-funny lines of dialogue that would make the sober viewer roll her eyes and surreal images or set pieces that seem entirely appropriate in only certain states of mind.

“Hot Tub Time Machine,” however, is being likened more to “The Hangover,” which very few people will argue for the status of a stoner comedy.

What about “Borat”? It made bank at the box office and quite the splash in the pop culture stratosphere, but where the hell does it fall in the comedy spectrum? It’s absurd, certainly, but its straightforward documentary style makes it seem like it’s something else entirely.

Then there are the Judd Apatow-directed, -produced, -inspired comedies that have been successful since “The 40-Year-Old Virgin.” Not absurd, but more firmly rooted in the contemporary pop culture mentality.

So many successful comedies, so few conclusions that they leave us with — except for one.

They all have MPAA ratings of R. And we’re not just talking about a little bit of blood and one f-bomb R-rated comedies — these are buckets-of-blood, tons-of-boobs and language-to-make-a-pirate-blush, hard R-comedies.

It may be nearly impossible to make distinctions on what types of comedies will be successful and what types won’t except to say that they need to be crass and that the more offensive the better.

Seriously, Zach Galifianakis’ handling of the abandoned stripper baby in “The Hangover”? Totally offensive to moms everywhere, and yet undeniably hilarious.

So, the U.S. has obviously gotten tired of s-words and proverbial above-the-bra-sexual content that runs rampant in pandering PG-13 rated drivel. “John Tucker Must Die” made a decent amount of money in the box office when it was released almost four years ago, but if it were to come out next week, that “Must” would most certainly be changed to a “Will.”

Do you remember “Dance Flick”? Of course you don’t. What about “The Love Guru”? Don’t make me LMFAO (see, I’m a hard-R columnist).

My theory for the shift in successful comedies lies in the recession and in how the mass entertainment audience is getting beat upside the head so hard by reality that a little vulgarity inserted into its entertainment resources comes as a welcome treat.

Or it may tie into the resurgence of the ’80s in our everyday pop culture lives. Leg warmers are back in style (I think) and synth-pop is in vogue (see my Goldfrapp “Head First” review), so it seems natural cinema is reaching out to the era of the pioneers of hard-R comedy, such as “Porky’s.”

Of course, this too might be symptomatic of the recession: Who doesn’t want to put himself in the state of mind of a time when consumerism and a thriving financial climate reigned supreme?

So as long as the films stay funny, and as long as they don’t compromise their vulgarity for sake of the box office, I will certainly buy into the idea of hot tub time travel. I’ll probably see the movie, too — twice.