Editor's note: This article may contain spoilers.
(CNN) -- It may not be conclusive proof of climate change, but every couple of years brings another "Ice Age" to air-conditioned multiplexes across the globe.
Each of its predecessors made more money than the one that came before, so there's an inevitability about this fourth venture -- "Ice Age: Continental Drift" -- even if it bears telltale signs of creative exhaustion and, yes, drift.
The franchise started out as a prehistoric, slapstick spin on the old John Ford western, "Three Godfathers," with a woolly mammoth, a sloth and a sabre-toothed tiger (Manny, Sid and Diego, voiced by Ray Romano, John Leguizamo and Denis Leary) delivering an orphaned human baby to safety. It has evolved -- or maybe "devolved" -- into a scrappy string of antic adventures interspersed with sitcom-style character notes, all pegged to whatever novelty the writing team can contrive in place of a plot.
In part three it was a subterranean dinosaur lair. In this episode, an unfortunate incident with an acorn at the earth's core precipitates tectonic realignment. When the continents part ways, Manny and the guys are trapped on an iceberg heading out to sea with only Sid's nutty grandmother (Wanda Sykes) for company.
Manny's quest to be reunited with wife Ellie (Queen Latifah) and teen daughter Peaches (Keke Palmer) is interrupted by a gang of scurvy pirates, led by a tricorn-headed orangutan, Captain Gutt (Peter Dinklage).
Whoever thought it was a good idea to spike this tired series with the defining component from a rival, equally over-extended franchise (not to mention the recent Aardman Animation pirate caper), well, here's a thought: maybe you could introduce a web-slinging spider-boy in the next one? You know, just to keep things fresh!
The animation is dynamic and crisp, but the story just runs around in circles while we wait for the sky to fall down. Truth be told, it's a kick that Twentieth Century Fox is distributing a movie about the dangers of climate change. "Doesn't it worry you that this is the end of the world?" someone asks a particularly unintelligent couple of party-hearty mammals. Uh-uh, they respond. "I guess we can tell you our secret... We're really, really stupid."
Like the equally stretched-to-the-breaking-point "Shrek" series, "Ice Age" has accumulated too many characters with too little to do, and all-star vocal stylings ("Continental Drift" adds Jennifer Lopez, Drake, Nick Frost and even Joy Behar, to name a few) can only do so much by way of compensation.
A bigger problem: the trio of reprobates at the center of proceedings have become so domesticated over the years, whatever mild comic edge they used to have has been dulled to a soft nub.
The loner, Manny, is now a boringly over-bearing father. The aggressive Diego is just a big pussycat. Only pea-brained Sid has stayed true to type, which will please infants more than their parents. (For the record, everything I disliked about this movie -- the dumb teen mammoth romance subplot, the narwhal-propelled iceberg, and especially the irritating Sid -- were selected as personal highlights by my 7-year-old.)
As in the earlier films, the most enterprising comedy features the mute squirrel, Scrat, who's Looney Tunes-inspired misadventures are almost always a welcome distraction -- even if we already saw too much of this material in teasers released last year.
Better than any of this is the five-minute 3D Simpsons short ("The Longest Daycare") that precedes the feature. A starring vehicle for baby Maggie, this is sharp, witty visual slapstick that harks back to the silent era for inspiration. True to form, my kid hated it.