Jack

In his career, Robin Williams has played an extraterrestrial, a Russian defector and a schizophrenic homeless man, all convincingly. So it's not surprising that he does so well as an overgrown 10-year-old in "Jack."

For about an hour, Williams' manic and funny performance actually sustains the film. But after that bit of silliness wears thin, the movie gradually erodes into little more than a "Big" wannabe that would be unwatchable without him.

And though the film's trailers advertise it as a family film, there's way too much crude humor, as well as profanity and violence, for it to really qualify as such.

Williams stars as the title character, a boy who ages four times faster than other children. So by the time he reaches 10, Jack appears to be 40 years old, complete with a 5 o'clock shadow and a receding hairline. But he also has a fifth-grader's playful intellect.

Because of his unusual appearance, Jack's parents (Brian Kerwin and Diane Lane) have made him a recluse who is feared by most of the neighbor kids. Even though he is spoiled by his family and has a wonderful tutor, Mr. Woodruff (Bill Cosby), the man-child craves the company of other children and finally convinces them to let him attend elementary school.

Once in school, Jack is shunned at first but eventually becomes friends with his classmates. But when his crush on his teacher (Jennifer Lopez, from "My Family") isn't returned, he suffers chest pains and has to return home.

This might all be refreshing if "Big" hadn't already been made years ago, and if the script didn't abruptly shift gears from a lightly comedic tone to truly maudlin melodrama.

While the movie would like to explore childhood and aging, it gets bogged down in juvenile "comedy" (a scene with both Williams and Cosby belching is just too awful for words) and sugary sentiments. For example, the film's sappy ending won't prompt any crying, unless it's tears from the unintentionally humor derived from it.

If parents thought "Welcome to the Dollhouse's" brutal portrayal of junior high was too unflattering, they'll be mortified by "Jack's" assertion that fifth-grade boys' minds are consumed with pornography and gross-out competitions (there are two extremely long and unfunny sequences dealing with flatulence).

Even worse, there are uncomfortable subplots about Jack buying naughty magazines for his newfound elementary school chums and about him going to a bar to drink, where he is seduced by one of his friends' mothers (Fran Drescher, as irritating as ever), who doesn't know how old he really is.

That's really unfortunate, because Williams is so wonderful. He really has the endearing, and sometimes aggravating, nuances of a young boy down. But director Francis Ford Coppola, who really should have known better, can't seem to figure out when to reel Williams back in. Certain scenes appear to be improvised, or perhaps screenwriters James DeMonaco and Gary Nadeau used William S. Burroughs' cut-and-paste method to assemble the script.

The film also wastes decent performances from Lane, Lopez and Cosby, who aren't given nearly enough to do - and frankly, Cosby should be embarrassed by the aforementioned belching scene.

"Jack" is rated PG-13 for vulgarity, profanity, violence and a nude female costume in one of the film's early scenes.