An idea whose time never should have come, "Dumb and Dumberer: When Harry Met Lloyd" traces the beginnings of the friendship immortalized in "Dumb and Dumber." Although it's set in Rhode Island, the favorite state of "Dumb and Dumber" creators Peter and Bobby Farrelly, the new comedy has little to do with its progenitor save for the names of its lead characters and the fact that each film was bankrolled by the same company, once out of inspiration and now, apparently, out of desperation.

The title almost says it all: Once upon a time, Harry meets Lloyd in high school; idiocy and the occasional joke ensue. A dim bulb radiantly inhabited by Jim Carrey before he became an Oscar hopeful, Lloyd is here played by Eric Christian Olsen, a young actor who manages a respectable impersonation of the older man in his ductile "Dumb and Dumber" mode. (Derek Richardson has Jeff Daniels' original role as the less flamboyant Harry.) Olsen can't approach Carrey's physical gifts or genius for excruciating embarrassment, but he does retain some of the character's freakish appeal. Blissfully unself-conscious, Lloyd has no sense of himself as a geek. He's securely locked inside his own head, a strange haven where he lives in a state of innocence, at once protected from the world and the more perilous repercussions of his own gross behavior.

Such benighted innocence is the not-so-secret heart of a lot of memorable comedy, from Laurel and Hardy to the first Harry and Lloyd. "Dumb and Dumberer" makes passing mention of Laurel and Hardy and tries to capture the Farrellys' anarchic giddiness, but it falls wildly short of its inspirations. That doesn't mean that there aren't funny bits or that the actors don't work hard -- only that making sport of other people's stupidity turns out to be pretty tricky. Director Troy Miller doesn't just lack the comic juice to extend his and co-writer Robert Brener's sketchy ideas into a feature, he's not above selling out his characters for a cheap laugh or two.

Unlike the Farrellys, who always grant a modicum of dignity to their creations, Miller and Brener exhibit something of a nasty streak. At the center of "Dumb and Dumberer" is the attempt by Harry and Lloyd's principal (Eugene Levy) to pull off a lucrative scam by establishing a "special needs" class. Just the mere suggestion that the two bunglers aren't just dumb and dumber but are, in fact, mentally retarded damages the film irreparably. The more Miller tries to squeeze humor from the principal's scheme, the queasier the jokes skew. The R word may never be voiced -- although one student goes so far as to ask Harry if he's "re-" before stopping herself mid-word -- but no matter. As Forrest Gump says, stupid is as stupid does.

'Dumb and Dumberer: When Harry Met Lloyd'

MPAA rating: PG-13, for crude and sex-related humor and language.

Times guidelines: Mild sex jokes; less mild scatological humor

Eric Christian Olsen ... Lloyd
Derek Richardson ... Harry
Eugene Levy ... Principal Collins
Rachel Nichols ... Jessica
Cheri Oteri ... Ms. Heller

New Line Cinema presents a Brad Krevoy/Charles B. Wessler/Steve Stabler and a Burg/Koules and Dakota Pictures production, released by New Line Cinema. Director Troy Miller. Writers Robert Brener, Troy Miller. Story by Robert Brener. Based on characters created by Peter Farrelly, Bennett Yellin, Bobby Farrelly. Producers Oren Koules, Charles B. Wessler, Brad Krevoy, Steve Stabler, Troy Miller. Director of photography Anthony B. Richmond. Editor Lawrence Jordan. Costume designer Susanna Puisto. Music Eban Schletter. Music supervisors Jonathan McHugh, Matthew Sullivan. Casting John Papsidera. Running time: 1 hour, 22 minutes.

In general release.