Which is to say that ''Ice Age: The Meltdown" is pure sequel product that should make children and undemanding grown-ups happy even as it lacks anything resembling storytelling inspiration. Anyone inclined to take the longer view may scratch his head and wonder why a kiddie movie is the only place our culture is willing to talk about global warming.
Yep, meteorological apocalypse is the dramatic engine of ''Meltdown" (are you ready for your Happy Meal?). The glaciers are retreating, oceans are breaking out everywhere, and all the baroque Pleistocene critters are rushing for the safety of a giant tree trunk ''ark" before a massive ice dam bursts and floods their valley.
Amid the glyptodonts, aurochs, and giant anteaters are a few familiar faces: Manny the mammoth (voice of Ray Romano), Sid the giant sloth (John Leguizamo), and Diego the saber-toothed tiger (Denis Leary). (Unlike in the first ''Ice Age," Paleolithic man is nowhere in evidence; presumably he has already made it to high ground.) These three form their own pack, although Manny is morose over the fact that he's probably the last of his kind.
Scratch that: Another mammoth appears in the form of Ellie (Queen Latifah), a high-spirited pachyderm convinced she's actually an opossum. The ''ugly marsupial" subplot extends to Ellie's romping blithely through the trees with her two adopted possum brothers, Crash (Seann William Scott, who played Stifler in the ''American Pie" movies) and Eddie (Josh Peck, from Nickelodeon's ''Drake and Josh"). These two come on like meerkats with attention-deficit disorder and are the second-funniest things in the movie.
The funniest -- by a long shot -- is Scrat, the prehistoric squirrel whose silent, increasingly desperate attempts to retrieve a precious acorn are dropped into the movie like ''Road Runner" shorts into a Cecil B. DeMille epic. Pared down to the bone of comic cause and hilarious effect, the Scrat sequences show off what mainstream CGI is capable of at its best: an unbeatable combination of hyper-realistic textures and crack Looney Tunes timing.
Elsewhere, ''Ice Age: The Meltdown" plods along with the heavy familiarity of Manny himself, introducing two thawed-out aquatic beasties to nip scarily at the heels of the heroes as they encounter one near-death experience after another. The saber-toothed tiger has to overcome his fear of water. Sid has to overcome his native stupidity -- no easy task -- and cope with a worshipful horde of miniature sloths who've apparently wandered over from ''Madagascar."
Manny, meanwhile, has to convince Ellie she's a mammoth for the greater good of the species, and only the geniality of Romano and Queen Latifah keep this plotline from devolving into an especially gooey episode of ''The Bachelor." Along with a crowd of cameo fauna -- Jay Leno as a fast-talking tortoise, Stephen Root as an aardvark, Will Arnett of ''Arrested Development" as a vulture -- they all move toward a climax of nearly biblical proportions, only to see the world saved by a tiny yet consequential act.
Well, it's a kids' movie; of course it's going to deal with climate change in a manner that's literally nuts. ''Ice Age: The Meltdown" raises a gnarly topical issue only to soothe it away, and you may wonder why the filmmakers brought it up in the first place. At least the script goes easy on the overbearing pop cross-references that bogged down ''Shark Tale" and ''Chicken Little," and the Scrat sequences are close to genius. My kids liked the movie ''better than the first one," and yours will probably play the DVD until the laser rots out of the player. That's what the studio is counting on. After the first spin, you won't even need to be in the room. After the third, neither will they.
Ty Burr can be reached at firstname.lastname@example.org.