Starring Harland Williams, Jessica Lundy and Beau Bridges Directed by Stuart Gillard Rated PG, with mild profanity and bodily-function humor Running time 101 minutes We give this film a rating of 5 out of 10

(Oct. 10, 1997) -- It's like the quest for the Holy Grail in Hollywood: the search for the next Jim Carrey.

Which, before Jim Carrey came along, was the search for the next Robin Williams -- which was the search for the next Jerry Lewis, ad infinitum back to the search for the next Charlie Chaplin.

But let's stick with the present, because the Carrey analogy is the most appropriate for Harland Williams, the unknown comic actor who is the star of Rocket Man. Obviously, the folks at Walt Disney Pictures are hoping Williams will pull an Ace Ventura and leap to the top of the box-office charts with this innocuous family comedy.

Well, sorry, but as inventive as Williams seems to be, he's no Carrey. The difference between Ace Ventura and Rocket Man is that in the original Ace Ventura Carrey took middling material and mined it for comic gold by sheer force of comedic will. Williams, who has a rubber face and physique, doesn't transcend this souped-up TV movie, despite a strong start.

The film's funniest sequence already has been milked to death in TV commercials: Williams, tethered by an oxygen hose to fellow astronaut William Sadler, passes gas, which then travels to his companion's suit. At the screening I saw, the kids were howling.

Williams plays Fred Z. Randall, a computer nerd who designed the software for the landing module of NASA's planned voyage to Mars. When one of the Mars-bound astronauts is incapacitated, Randall is tapped to fill his place, despite his numerous and very apparent shortcomings. Inevitably, Fred screws up all the way to the film's climax -- and then comes through with flying colors.

This is the kind of forgettable family fare that Disney made much of in the 1960s. In those days, it usually starred someone like Tim Conway or Don Knotts in the lead role and quickly found its way to Disney's weekly TV show.

Williams is saddled with an unfunny catch phrase ("It wasn't me," he yelps whenever he makes an obvious miscue) and some bizarre sequences, apparently calculated to play to his comic strengths. In one, he is aced out of his hypersleep chamber by the resident chimp and is forced to entertain himself for the eight-month voyage while the other crew members doze. It's a surreal stretch, one filled with pop-culture references guaranteed to fly right over most kids' heads.

If you don't mind humor about flatulence, there's nothing objectionable for children, at whom this film is pitched (though those under age 8 may grow restless). But parents may find Rocket Man to be one of those films they skip and leave to the small-fry audience.