The inexplicably popular live action/animated series featuring a bevy of screechy-voiced singing rodents reaches its third—and one fervently hopes, final—installment with “Alvin and the Chipmunks: Chipwretched,” which is certainly the runt of the litter so far, but equally certain to draw large audiences.

After sitting out the first sequel, Jason Lee returns as Dave Seville, the guardian/father figure to the three Chipmunks—Alvin (Justin Long), Simon (Matthew Gray Gubler) and Theodore (Jesse McCartney)—who originated as a novelty record act in the 1950s and returned in computer-animated form in 2007. He and the “boys” are now accompanied by the Chipettes—Brittany (Christina Applegate), Eleanor (Amy Poehler) and Jeanette (Anna Faris)—introduced in the second installment.

As the picture opens they’re all boarding a Carnival cruise ship for a vacation. Of course, Alvin disobeys Dave’s orders to behave himself, and the others—except for Theodore—follow suit, scampering off to cavort in the ship’s casino and causing all sorts of trouble that earn a stern rebuke from the captain. The last straw comes when Alvin’s toying with a kite sends all six chipmunks airborne onto a deserted island. Dave soon follows, accompanied by his old nemesis Ian (David Cross), who’s been reduced to playing a kid-friendly chicken on the cruise. On the island the band encounter a long-marooned castaway (Jenny Slate) who—in one of the script’s most obvious gags—has gone off the deep end and adopted a variety of balls, Tom Hanks style, as her companions. And straightlaced Simon is transformed into the reckless Simone (voiced by Alan Tudyk). There are also a treasure hidden away in the caverns and—of course—a suddenly active volcano on hand.

Tots of a certain age—those in single digits—will probably enjoy the antics of Alvin and his crew, though the time given over to Dave and Ian—even with their slapstick bits—will probably try their patience. But at times the movie simply goes beyond the pale, as in all the stuff involving Slate (who turns into a raving maniac at the close, occasioning a big last-act rescue sequence) and, toward the beginning, in an almost surrealistically weird dance-off between the Chipettes and a trio of sultry broads in the ship’s casino.

And even if one can tolerate the straight comic stuff, you still have to deal with the Chipmunks’ ear-splitting singing, which erupts at every conceivable opportunity. Actually the tune selection isn’t bad, and some of the titles even cheekily comment on the action (certainly better than the dialogue, which basically consists of lame one-liners and even hoary pop-culture references, like the one to “Cast Away”). But the speeded-up vocals insure that every instant of them will be insufferable.

At the risk of spoiling the surprise, all the critters—human and animal—are saved at the conclusion of “Chipwrecked.” Some viewers are apt to be very disappointed by that.