'Hot Tub Time Machine 2' goes back to the future — and the past

At the end of the first, often crudely funny time-travel comedy “Hot Tub Time Machine,” when Craig Robinson's character cracked that, “This better be the last time my (butt) travels through space,” no one in the audience took him at his word. That 2010 film, in which a group of 40-ish bros revisit one wild weekend of their misspent youth via the time portal of a malfunctioning hot tub, practically cried out for a sequel.

And sure enough, “Hot Tub Time Machine 2” opens with Nick (Robinson) asking his reprobate buddy Lou (Rob Corddry) whether he, too, ever wishes that he could “go back for one more dip” to “tweak” some things.

Fire up the bubbles (which in this case come courtesy of a flatulent presumed corpse). Most of the first film's protagonists — Robinson, Corddry and Clark Duke, but not John Cusack, who politely declined to return to his role as the normal guy — have plunged, headfirst, into the rank waters of the amusing if somewhat less than hilarious sequel, which takes the boys into the future to solve the attempted murder of Lou, which opens the film. In a nod to the “Terminator” movies — one of a myriad cinematic references that litter the new movie, like buckshot from screenwriter Josh Heald's unsubtle pen — the assassin seems to be a time traveler from the year 2025.

This gimmick offers returning director Steve Pink an opportunity to riff a bit on technology and culture: crass reality TV shows (or, rather, virtual-reality TV shows), smart cars and the increasing loss of privacy. But like the first film, which only glancingly mocked the 1980s, “Hot Tub Time Machine 2” isn't interested in social satire. It's a parade of penis jokes — the film almost literally opens with the sight of male genitalia — interspersed with a halfhearted murder investigation.

Assisting in the sleuthing is Adam Scott, who plays the namesake son of Cusack's missing character, Adam. Exactly how the elder Adam has a forty-something son, when the previous film did not indicate his presence, isn't explained. Both films play fast and loose with time, and it seems Cusack's character, whose life course was altered by the action of the earlier film, has now spawned.

At the end of the 2010 film, Lou was the billionaire inventor of the search engine Lougle. In 2025, his son (Duke) appears to be the tech magnate, while Lou is an almost homeless addict. Nick, a singer and record producer, has made a career out of stealing pop songs that haven't been written yet. They include “Stay,” by Lisa Loeb, who makes a game cameo as a cat wrangler on the set of Nick's music video for that ditty, which includes his own nonsense lyrics. It's kind of funny.

It's also a bit confusing. How is it that “Stay” — a hit for Loeb 20 years ago — hasn't yet been written? Never mind. Just keep moving on to the next example of phallocentric humor. “Hot Tub Time Machine 2” is a guy's film, assuming that guy is (or has the mentality of) a teenage boy. Most of its jokes never stray very far from the male crotch, except for the occasional excursion to the land of female anatomy, which appears to be a terra incognita, given the sense of adolescent wonder with which “Hot Tub Time Machine 2” presents the sight of a woman's bare breasts.

The film isn't bad, although it is somewhat repetitive. If it has plot holes, conceptual laziness and an overreliance on dumb-insult humor, it at least seems to know it. There are lots of self-referential jokes that acknowledge its own stupidity.

“Hot Tub Time Machine 2” also knows its audience. And they know who they are. If you have to ask yourself whether this film is for you, it isn't.