Relentlessly good-natured and endlessly predictable, Tim Allen’s new comedy is essentially an elongated episode a typical television sitcom–understandable, perhaps, given how the star rose to fame, but hardly fair in light of today’s rising ticket prices and concession stand costs. “Joe Somebody” is innocuous and instantly forgettable; it isn’t harmful or ugly, but despite its title, it goes nowhere at all.

In John Scott Shepherd’s entirely formulaic script, Joe Scheffer (Allen) is a recently-divorced milquetoast working in the commercials department of a Minnesota pharmaceutical firm. He’s devoted to his precocious daughter Natalie (Hayden Panettiere) and still smarting over the loss of his stage-struck wife Callie (Kelly Lynch); at work he’s tormented by smarmy Human Resources head Jeremy (Greg Germann) and ignored by virtually everyone else, although Jeremy’s assistant, sweet Meg Harper (Julie Bowen), finds him charmingly klutzy. The plot kicks in when the company’s resident beefy jerk, Mark (Patrick Warburton) nonchalantly clobbers Joe in front of Natalie in an argument over a parking space. Joe goes into a temporary funk which even Meg’s intervention can’t help, but he snaps out of it when he decides to challenge Mark to a rematch. He tries to buff up, beginning karate lessons with Chuck (Jim Belushi), a drugged-out guy who used to star in grade-Z fight movies with titles like “Tom Sawyer Must Die!” When his co-workers hear about his plans, Joe becomes an instant celebrity, and he responds by undergoing a personality makeover, complete with new wardrobe. His transformation gets him lots of recognition, and even a promotion. Only Meg and Natalie are concerned that he’s not being true to his nice, lovable self and argue that fisticuffs aren’t the answer, but Joe’s so gratified by all the attention, and made so confident by his progress under Chuck’s tutelage, that he’s reluctant to revert to his old persona, even though his growing romantic interest in Meg pushes him in that direction.

You can almost imagine this feeble plot being played out over the half-hour span of a mediocre network comedy (like the one Belushi’s starring in with surprising success right now, for example); when drawn out to a hundred minutes, it seems cruelly protracted. A great deal of time is devoted to scenes of Joe preening himself before the bathroom mirror and indulging in all sorts of ham-fisted slapstick in his training with Chuck; blows to the groin are regular occurrences–the ultimate proof of lazy scripting. Other comic set-pieces abound, too, most notably a silly game of squash which employs a good deal of amateurish trick photography, and there’s the requisite assortment of tepid romantic moments, too. The picture tries to generate some suspense–will Joe fight Mark? will he link up with Meg, or go back to Callie? can Natalie come out of her scholastic funk?–but it resolves them all no more ingeniously than would have been the case on “Leave It to Beaver.” Regarding the fight, the denouement is pretty much a cheat, effectively going both ways to satisfy the audience’s hunger for a little action while piously upholding a preference for a peaceful way out.

Allen works hard to put this stuff across, and he sometimes succeeds–especially in the sequences with Belushi, which may be obvious but garner some easy laughs. There are also occasional bits of dialogue that earn a chuckle or two–for example, a couple of snippets from the “warning” sections of TV commercials for the firm’s drugs near the beginning of the flick are pretty funny. But for the most part the material is flat, and it’s flatly played. Apart from Belushi, the supporting cast is tepid, with both Bowen and Lynch making very modest impressions (a “victory dance” that the former does after a basketball game with some young girls is acutely embarrassing) and both Germann and Warburton very badly used. Panettiere isn’t quite as insufferable as most kid actors, but she comes close. And Jesse Ventura, heaven help us, makes a brief and pointless cameo appearance; it’s nice that he should do his best to promote film production in his state, but neither this picture nor his participation is likely to help the cause much. Technically “Joe Somebody” is at best mediocre–the Minnesota setting certainly isn’t employed to any advantage–and George Clinton’s music score is overly intrusive, especially toward the close.

Tim Allen’s movie career hasn’t exactly skyrocketed since his debut in “The Santa Clause” (1994). One of his recent projects, “Big Trouble,” which was supposed to be released a few months back, was postponed in light of the events of September 11 because of some plot elements, and the present effort is too feeble to attract many viewers. Maybe a return to the tube would be in order.