"Dumb and Dumberer" is a prequel to the Farrelly brothers' 1994 surprise hit that starred Jim Carrey and Jeff Daniels as lamebrained pals on a cross-country road trip. Look at it as that rare case of truth in advertising, since the new movie is indeed more moronic than the original.

Of course, that's the point. Carrey and Daniels are here in caricature only; actors Derek Richardson and Eric Christian Olsen play Harry and Lloyd as high school dorks in 1986, enrolled in a "special-needs" class that doesn't really exist. It's simply another scheme by the evil Principal Collins (the often ill-used Eugene Levy), this time to bilk the school out of the $100,000 grant for a special-education program.

Collins enlists his lunch-lady girlfriend (Cheri Oteri) to teach the class, held in a tool shed. Harry and Lloyd, meanwhile, are sent to find other misfits to fill the roster, and come up with a Mohawk-wearing Turk (Elden Henson) and a foreign-exchange student named Ching Chong (Michelle Krusiec).

When a crusading student reporter (model Rachel Nichols) thinks she smells a scoop, she makes separate dates with the boys to find out what they know, which isn't much. The guys think she is coming on to them; in the movie's comic set piece, a Hershey bar melts in Harry's pocket and somehow ends up all over her parents' pristine bathroom.

For the most part the young actors are pretty good at mimicking the recognizable stars, especially Olsen in the Carrey part, complete with bowl haircut and chipped front tooth. Squint a bit harder and you'll see Daniels beneath Richardson's mop of stringy blond hair.

Director Troy Miller ("Jack Frost") is less effective at channeling the hit-and-miss, try-anything charm of "Dumb and Dumber," which was the first in a long line of self-consciously stupid comedies that even the Farrellys have forgotten how to make very well.

A dumbed-down version of something that was stupid to begin with, "Dumb and Dumberer" is intended as a tribute to the Farrellys. Instead it makes a salient point about the pathetic state of Hollywood comedies for which the brothers are blamed.