Night at the Museum

“Night at the Museum” has a premise that sounds fantastic until you look closely at it. It’s about a security guard at a large museum who discovers his first night on the job that between sunset and sunrise, everything in the place comes to life. A little close to “Jumanji,” sure, but that’s workable.

The problem is, where can you go with such a premise? Any scenes set outside the museum, or set inside the museum during daylight hours, will seem irrelevant. Why waste our time with other stuff when there are living dioramas and T-rex skeletons to look at? And furthermore, what’s the actual story going to be? “A museum where the exhibits come to life” isn’t a plot; it’s a premise. You have to DO something with it to turn it into a plot.

The “Night at the Museum” writers — the hacktastic duo of Ben Garant and Thomas Lennon (both so funny as actors on “Reno 911,” and so bad as writers of family dreck like “The Pacifier” and “Herbie Fully Loaded”) — have fleshed out Milan Trenc’s children’s book to include a trio of retiring security guards (Dick Van Dyke, Mickey Rooney, and Bill Cobbs) who tell the new guy, Larry (Ben Stiller), the source of the museum’s mysterious power. They also provide conflict when they try to snag that power for themselves.

It’s the first special-effects-heavy comedy for star Ben Stiller or director Shawn Levy (“Cheaper by the Dozen,” “The Pink Panther”), but both adapt rather well. Perhaps because the many digital effects make rampant improvisation too expensive, Stiller is much more subdued than usual, with the resultant performance far more likable than when he’s sweatily trying to get laughs. Levy, for his part, keeps the pace brisk and the storytelling simple.

The museum has a wide range of exhibits, including dioramas with miniature Old West figures and ancient Roman warriors. When they come to life, the tiny li’l fellas — Jedediah (Owen Wilson) the cowboy and Octavius (Steve Coogan) the Roman — fight with each other rather amusingly and lead their Lilliputian forces to attack Larry.

On the life-size level, there are Huns, lots of ferocious African mammals, and a wax figure of Teddy Roosevelt (Robin Williams) who has long pined for the wax figure of Sacagawea (Mizuo Peck). Larry interacts with all of these and more, at first unable to control the chaos that ensues every time the sun sets, but soon taking command and governing his charges like a general.

Nearly everything else about the movie is negligible. That includes Larry’s scenes trying to make his young son Nick (Jake Cherry) look up to him, and his attempts to befriend and impress a docent (Carla Gugino). So, too, are the half-hearted attempts to make it look like Larry has taken control of the late-night chaos by learning and applying history. Who made the rule that “family movies” must be filled with treacly sentiment and life lessons? Can’t a guy just run around a museum being pursued by reanimated mastodons and wax-figure Neanderthals? When that’s the order of business, “Night at the Museum” is fine.

B- (1 hr., 48 min.; PG, a little very mild profanity, mild action-related violence.)