Why do they keep doing this? Why do they keep brewing up movies from the soggy dregs of old '60s TV series? Like other such awkward projects ("Wild Wild West," "The Avengers"), the new "Get Smart" is uncertain exactly what it wants to be. The original show, created by gag maestros Mel Brooks and Buck Henry, began airing in 1965, in the midst of a spy-movie craze that had been launched by the first three Bond films. That very particular cultural context being long gone, this movie is left with a narrative premise — secret spy agency battles international bad guys with a barrage of shpritzy one-liners — that has no contemporary cognate. And so the filmmakers have striven mightily to refashion their antique material into something, anything, else. What they've come up with is an uneasy amalgam of slapstick comedy, half-hearted romance and, most desperately, rampaging action. The picture is funnier than you might expect, though, and if your expectations are bare-minimal, it might occasionally pass for hilarious.

Fans of the original TV show may be puzzled by this lackluster update (it's not worth getting angry about). But of course they aren't the film's target demo, which is a new audience that's too young to remember the old series and must therefore be courted with more up-to-date inducements. Fortunately, the movie has a sharp cast: Steve Carell as the bumbling spy Maxwell Smart, Anne Hathaway as the beautiful Agent 99, Dwayne "The Rock" Johnson (his old wrestling handle soon to be an unnecessary credits appendage) as the stalwart Agent 23, and Alan Arkin as their flustered chief, Chief. A few tokens of the old series have been carried over: Maxwell's silly shoe phone, the malfunctioning Cone of Silence, the telephone-booth entrance to the headquarters of the underground agency, which is still called CONTROL (an acronym that still stands for nothing). But there's no attempt to simulate the '60s: The story has been updated to the age of the iPod. Unfortunately, this adds a new layer of implausibility to a tale that was only loosely moored in any recognizable reality to begin with.

The gags that work, however, are almost worth sitting through the ones that don't. (Maxwell's acing of an agency test with an essay on existentialism — even though, as he says, "I left that section blank" — has the shape of a joke, but doesn't scan when you think about it.) There's plenty of vintage ba-da-bing ("Welcome back. How was the assassination?"), and Carell's gift for physical comedy puts across such slapstick set pieces as a one-man mini-crossbow struggle in an airplane lavatory (don't ask) and an elaborate and surprisingly sweet dance-off in which he partners with the very large and entirely lovable actress Lindsay Hollister. Johnson once again demonstrates a precise light-comic touch; and the veteran Arkin, now 74, has, of all things, a couple of funny fight scenes.

Unfortunately, Hathaway's character — here upgraded from the adoring sidekick of the TV show to a thoroughly modern butt-kicker — is written with blithe disregard for the need to make at least a little bit of sense. She spends most of the movie sneering at Maxwell, her unwanted new partner, and then, for no persuasive reason, suddenly falls in love with him. Since Hathaway and Carell have no particular romantic chemistry, this attempt at forcing a relationship is a watch-checking waste of time. Hathaway is too talented to be given such short shrift.

As for the plot, well, it's something about a terrorist scheme to nuke the president of the United States (James Caan, putting in a pointless appearance) during a symphony concert in Los Angeles. (Los Angeles?) The terrorists here are a vaguely constituted crew of goons bearing no resemblance to the terrorists we know so well today. These people, members of the rival spy agency KAOS, are Russians (I think), although they're led by a character named Siegfried (Terence Stamp, underutilized), who appears to be German. By about halfway through the movie, this strained scenario begins to drag woefully. And a sudden avalanche of road-chase action at the end, despite some impressive stunt work, is a big-bucks climax that seems to come careening in from another movie. Not necessarily a better one, either.

"Get Smart" is a piffling summer diversion. Unsurprisingly, Steve Carell is the best reason to see it. But even his distinctive comic persona — the deeply deadpan puzzlement, the occasional, unexpected glow of human warmth — may not be reason enough.

Check out everything we've got on "Get Smart."

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