There aren’t many movies that call out for sequels, but “Dumb and Dumber” would be near the bottom of most people’s lists. The 1994 Farrelly brothers’ slapstick comedy was sub-Three Stooges material that, in terms of gross-out status, aimed lower than low, and a 2003 prequel, “Dumb and Dumberer,” was so dismal that even audiences attuned to such stuff stayed away in droves.

Still, one can understand why the makers of the original should have decided to return to this barren well again. The careers of Bobby and Peter Farrelly have pretty much stalled over the last couple of decades, and neither Jim Carrey nor Jeff Daniels has exactly been riding high either. Why not attempt to return to the glory days?

“Dumb and Dumber To” explains why. It begins with Lloyd (Carrey) ensconced in a catatonic state at a rest home, supposedly as a result of being jilted two decades earlier, where he’s regularly visited by old pal Harry (Daniels). But after Harry announces that he has a medical problem that will keep him from coming any longer (a statement that’s frankly at odds with the movie’s big final revelation, but who cares?), Lloyd awakens (a joke that won’t be explained here) and the two become buddies tied at the hip again.

After a brief reunion with Harry’s parents (during which he’s told that the Asian couple aren’t his biological mom and dad, much to his chagrin—shades of “The Jerk”), the two set off on an adventure to track down the daughter Harry’s just discovered he sired by town tramp Fraida (Kathleen Turner, looking the worse for wear). They learn that the girl, Penny (Rachel Melvin), was adopted by Dr. Pinchlow (Steve Tom), a noted scientist, but at the moment has gone to deliver a box containing a valuable secret to the organizers of a conference in California. What they don’t know is that Pinchlow’s wife Adele (Laurie Holden) is plotting to kill him with the help of handyman Travis (Rob Riggle), who’s sent along with the boys on their trek west to dispose of them, too. The action eventually winds up at the California conference, where Adele and Travis’ twin brother, a military superspy, also show up. Much slapstick mayhem and a number of odd revelations ensue, in which Riggle—stuck not just in one terrible part but two—suffers most (apart from the audience, that is).

As in the first movie, the ramshackle plot is nothing more than an excuse for Daniels, and especially Carrey, to exhibit their knack for acting very stupid, often in ways that involve knockabout comic pratfalls. Even if one found their shenanigans less than hilarious twenty years ago, they were easier to take back then because the duo were younger and seemed more resilient in the face of physical damage. Now, with both actors in their fifties, you’re likely to be more worried that they might suffer actual bodily harm than amused by their antics. (Watching Moe, Larry and Shemp—or even worse, Joe Besser or Joe DeRita—pummeling one another when they’d grown long in the tooth is likely to make you cringe, too.)

Otherwise “Dumb and Dumber To” traffics in lots of potty humor—fart gags abound, of course—though none of it can match the literally execrable bathroom scene Daniels (and the audience) endured in the first movie. It’s also a problem that some of the shtick that Lloyd, in particular, engages in is so mean-spirited. That’s especially the case with the material at the start involving blind Billy (Brady Bluhm), but the nasty attitude is perceptible elsewhere too, and efforts to add a bit of sentiment from time to time don’t really mitigate it.

It does have to be said that Carrey and Daniels throw themselves into the spirit of things with an abandon that belies their years, and the Farrellys—along with co-writers Sean Anders, Mike Cerrone, John Morris and Bennett Yellin—certainly pile on routines designed to recapture the anarchic spirit of two decades ago. But what came across as edgily over-the-top in 1994 seems almost passé in the era of Adam Sandler and Judd Apatow, not to mention Johnny Knoxville and his Jackass crew. And the efforts of those both behind and in front of the camera carry a feeling of over-the-hill desperation, of trying to recapture a magic that’s long since dissipated. The sense that this stuff has long passed its expiration date is reflected in a physical production that looks tired and pro-forma, too.

This is a movie guaranteed to make you feel dumber than you did when you plunked down money to see it.