Cheaper by the Dozen 2

Where: Theaters everywhere.

When: Opens today.

Rating: PG for some crude humor and mild language.

Running time: 95 minutes.

Bottom line: Steve Martin, Bonnie Hunt and their many kids are back for another round of slapstick comedy.

If anyone ever thought Ashton Kutcher was as dumb as the characters he usually plays, this should brand him the smartest person in Hollywood: He stayed far, far away from "Cheaper by the Dozen 2," a painfully forced sequel to the 2003 family comedy.

In the first movie, Kutcher's Bud McNulty married Nora (Piper Perabo), the oldest of 12 kids raised by the hard-charging Tom (Steve Martin) and the easygoing Kate (Bonnie Hunt). The sequel begins with the Bakers in transition: Nora is pregnant, and she and Bud (now played by Jonathan Bennett) are about to leave Chicago for Houston; oldest son Charlie ("Smallville's" Tom Welling) is mulling his college options; and super-shallow daughter Lorraine (Hilary Duff) has graduated from high school and will soon move to New York for a fashion-magazine internship.

The Bakers decide they need one last summer vacation like they used to have, at the old cabin on Wisconsin's Lake Winnetka. They arrive to find that Tom's old rival, Jimmy Murtaugh (Eugene Levy), has a huge lakefront cabin and a trophy wife (Carmen Electra), and his eight kids have all the cool toys. Tom and Jimmy get competitive all over again, even as their kids start pairing up - Charlie with the unhappily overachieving Anne (Jaime King), and 12-year-old Sarah (Alyson Stoner) getting her first crush on cute Elliott (former SharkBoy Taylor Lautner).

With all these characters and subplots fighting for screen time, it's a wonder that director Adam Shankman (who directed Martin and Levy in "Bringing Down the House") also can cram in nutty slapstick, an exploding outboard motor, a packrat in the floorboards, a guy in a wheelchair getting pushed into the lake (twice!) and enough heart-to-heart talks to fill an episode of "Dr. Phil."

Unfortunately, the humor in Sam Harper's script is as malnourished as Hilary Duff appears to be. (The actress/pop star looks so thin that you fear for her health, which is a major distraction for a featherweight comedy.) And if you can hear the gears grinding during the funny bits, that's nothing to the sputtering mechanics of the heart-tugging moments - and together, the clunkiness makes "Cheaper by the Dozen 2" a vehicle that isn't going anywhere.

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