A walk along the pier to their cruise ship while belting out a naturally high-pitched rendition of The Go-Go's "Vacation" is how "Alvin and the Chipmunks: Chipwrecked" kicks off, and it is so no-nonsense and direct that it's almost jarring. Is the first reel missing? Or does director Mike Mitchell (2010's "Shrek Forever After") and writers Jonathan Aibel & Glenn Berger (2011's "Kung Fu Panda 2") figure that, by the rodents' third live-action/computer-animated amalgamation, audiences are already familiar with the characters and don't necessarily need a tidy set-up? Then again, that doesn't stop all of the above from milking 87 minutes out of a plot so shallow it's long grown stale and tedious by the one-hour mark. Therein lies the problem. While this entry blessedly does away with most of the unsettling and mean-spirited themes of the earlier films—namely, the exploitation of children and the hypocrisy of deriding mass-market corporations and shameless product-placement while being itself a mainstream entertainment in existence for the sole purpose of making money and selling merchandise—there simply isn't enough material to withstand a feature-length running time in between the musical numbers. For what it's worth (not much), it's still the best of the trilogy.

Dave Seville (Jason Lee) is looking to kick back and take it easy on a tropical cruise with his six adopted chipmunks—young teens Alvin (indistinguishably voiced by Justin Long), Simon (Matthew Gray Gubler), Theodore (Jesse McCartney), Brittany (Christina Applegate), Jeanette (Anna Faris) and Eleanor (Amy Poehler)—but trouble-making leader Alvin is making it especially difficult for him to relax. A kite-flying incident soon after sends the chipmunks blown away and stranded on an island, seemingly deserted by everyone but loopy mail-carrier castaway Zoe (Jenny Slate) and her assortment of inanimate ball friends. As they hold on to hope that their human father will rescue them—everyone, that is, but Alvin, who thinks he's too much of a pain to be wanted—a volcano gurgles and smokes nearby, threatening to erupt any minute. Meanwhile, Dave and Ian (David Cross), the latter a former crooked record label producer who now gets work as a pelican mascot, set out in hot pursuit to bring them home.

"Alvin and the Chipmunks: Chipwrecked" is more of the same when it comes to time-sensitive pop-culture references (e.g., Charlie Sheen's "Winning!" catchphrase and "Double Rainbow"/"Honey Badger" YouTube clips get moments in the spotlight, while Theodore says at one point, "You can follow me on Critter!") and predictable movie spoofs that will go right over the kids' heads (James Bond's "shaken, not stirred" line gets tweaked and 2000's "Cast Away" is aped multiple times). What they'll get out of it is simply the diversion of watching some cute, pint-sized, domesticated woodland creatures sing and dance around to the latest pop hits by Lady Gaga ("Bad Romance" and "Born This Way"), Katy Perry ("Firework"), LMFAO ("Party Rock Anthem"), Willow Smith ("Whip My Hair"), and Michael Franti ("Say Hey (I Love You)"). That's really all there is to it, with subplots feeling either derivative (like the squabble between Alvin and Dave that leaves the little guy thinking he's not loved anymore) or purely like afterthoughts (hidden jewels that temporarily turn Zoe into a crazed treasure hunter). As for the volcano, it ominously threatens eruption for so long that the viewer finally starts hoping for some hot lava murder just so the movie will end soon.

With TV's now-cancelled "My Name Is Earl" no longer bringing in a steady paycheck for Jason Lee (2010's "Cop Out"), the actor has gone from a cameo appearance in 2009's "Alvin and the Chipmunks: The Squeakquel" to significantly increased visibility here. Dave is a genial but thankless part, and Lee too frequently is called upon to just do a lot of yelling and exaggerated hand-waving. New to the series, former "Saturday Night Live" member Jenny Slate makes the most of Zoe in the same way Anna Faris excelled beyond the limited confines of 2010's "Yogi Bear." Slate's facial expressions and sharp timing earn a few of the film's sporadic laughs. Also, still the best of the chipmunks is the big-boned, good-hearted, and adorably vulnerable Theodore, who gets more than he bargained for when he sits down in their cruise ship cabin to watch "Jungle Monster 4." The names who voice the chipmunks, as usual, are done no favors by a post-production process that renders them all to sound like a sped-up record player. Since it is impossible to recognize their voices, what is the point?

"Alvin and the Chipmunks: Chipwrecked" might have been wise to do away with the wreck. Most of the best scenes are early on as they have fun and wreak havoc on the cruise ship. When the Chipette's find themselves in a dance-off with three spicy women at a club ("You better get those sorry press-on nails out of my face!" Brittany sasses to one of them), it's silly, cute and energetic. Once swept away to the island, the picture loses a lot of its inspiration and can never quite figure out what to do with the characters from this point forward. Significantly padded, the film gets mighty interminable by the third act, only jumping back to life in time for a final medley performed at the International Music Awards. Children won't get much use out of the lightweight "Alvin and the Chipmunks: Chipwrecked," but it should keep them quiet for nearly an hour and a half. That may be enough of an incentive for parents to take them to see it. Otherwise, keep moving.