OK, so what if a bumbling night watchman at the Museum of Natural History unleashed an ancient Egyptian spell that lets all the animals and historical figures break free from their display cases and come to life?

	A legion of Roman Gladiators prepares to wage war on museum security guard Ben Stiller in "Night at the Museum." Click photo for larger image. 'Night at the Museum' Starring: Ben Stiller, Robin Williams, Dick Van Dyke, Mickey Rooney. Director: Shawn Levy. Rating: PG for mild action, language and brief rude humor. Web site: http://www.nightatthemuseum.com/

In that case, and out of those cases, you'd get a helluva "Night at the Museum." It begins with divorced dad Ben Stiller, endless purveyor of failed schemes, worrying that his son will reject him for new Wall Street dad (Paul Rudd). Ben still dreams of doing something big. "But what if you're wrong?" asks the kid, who is nobody's fool. "What if you're just an ordinary guy who should get a regular job?"

Well might he ask. On his father's museum watch, things go more than just "bump" in the night. Mayas, Roman gladiators and cowboys leap from their dioramas to battle one another. Neanderthals, in their quest for fire, nearly burn down the whole museum. Attila the Hun pillages his next-door-neighboring exhibits, while an overly frisky Tyrannosaurus rex runs amok (but secretly just wants to play fetch).

Cardboard villains of the piece are Stiller's predecessor security guards at the New York museum, Dick Van Dyke and Mickey Rooney -- museum exhibits in their own right. Actually, the always enjoyable Van Dyke is lookin' good. But Mickey Rooney, at 86, isn't.

Turns out, the only person who can save the situation is President Theodore Roosevelt (Robin Williams) -- or, rather, the waxwork figure thereof -- who helps Stiller gain control of the chaos, even as Teddy longs for beautiful Sacajawea (Mizuo Peck) in a display case nearby. Williams does his sincere best under ridiculous circumstances.

Director Shawn Levy (guilty of the recent abysmal "Pink Panther" remake) and screenwriters Thomas Lennon and Robert Garant owe more than a nod to "Jumanji" (1995), whose concept was an animal board game come to life. The film at hand isn't about story or characters or messages or anything other than racing from one set of (admittedly fine) special F/X to another.

It is periodically entertaining, thanks in part to the funny love-hate relationship between a miniature cowboy (Owen Wilson) and miniature Roman general Octavius (Steve Coogan), whose Lilliputian high jinks are capped by Wilson's soulful throwaway line, "I ain't quittin' you."

But let's dare to say it: Despite his success in "Meet the Fockers" and the "Parents" et al., Ben Stiller is just not very hilarious (in general), and neither is this script (in particular). His best scene here involves a capuchin monkey slapping him silly (after biting his nose and peeing on him). If that's your idea of riotous, go for it. If not, consider avoiding it like the plague.

Well, all right, "Night at the Museum" is just a harmless kid-flick holiday movie. There were abundant laughs at the preview screening. But I'd much rather have spent a night at the opera.