In Ice Age: The Meltdown—as in its hit 2002 predecessor—the opening and closing sequences are devoted to the misadventures of the twitchy, acorn-obsessed rodent known as Scrat. He appears in interstitial segments throughout the feature as well, but it’s most noteworthy that the filmmakers lead and close on this funky supporting character rather than their ostensible protagonists. Everyone knows he’s the real star of the show—including 20th Century Fox, whose marketing department wisely made Scrat the central figure in the film’s poster art. He’s there to warm up the audience and to send them out on a comedic high—because he’s not just the best thing about the Ice Age movies, he may be the funniest cartoon character created since the zenith of Chuck Jones.

There’s a level of creativity involved in the Scrat segments—pure visual slapstick artistry—that bears comparison not just to the heyday of the Coyote and Road Runner, but to Buster Keaton and Charlie Chaplin. It’s something rarely even attempted in an era when the goal of animated filmmaking often seems to be cramming in as much mile-a-minute, gag-laden dialogue as possible between the poop jokes. And if the creators of Ice Age devoted even half as much energy and invention to the main story as they did to Scrat, we’d be talking about a classic for the ages instead of a lot of dead air between moments of brilliance.

Like the original Ice Age, the sequel is in many ways a celebration of the kind of unconventional families that don’t fit the red-state profile. Phlegmatic mammoth Manny (Ray Romano), saber-toothed tiger Diego (Denis Leary) and simple-minded sloth Sid (John Leguizam) are still hanging out together, but their little valley appears threatened by global warming if an ice dam yields to the wall of water behind it. As they head for higher ground, the threesome meet up with Ellie (Queen Latifah), a mammoth who thinks she’s a possum because she grew up with adopted brothers Crash (Seann William Scott) and Eddie (Josh Peck). They join forces in their scramble for safety, a weird little romance developing between Manny and the potential mate who may be the last female of his kind.

It might seem a bit strange to build the premise of what is ostensibly a family film around the possibility of species-saving procreation, but I suppose it’s just the latest evolution in what is presented as appropriate for kids. Ice Age: The Meltdown comes with a PG rating, and it earns every ounce of it; the first 15 minutes aren’t in the books before gags built around the words “dam”, “ass” and “crap.” If the parents of America make this a blockbuster hit by bringing along their pre-schoolers just because the characters appear on packages of fruit snacks, I don’t want to hear another peep about the coarsening of our culture for at least a decade.

But aside from being crude, Meltdown just isn’t particularly interesting. The plot of the original may have just been the umpteenth iteration on the 3 Godfathers plot that has involved everyone from John Wayne to Steve Guttenberg over the years, but upon subsequent viewings its simple charms have grown on me. The sequel lacks not just a genuine antagonist—while climate change may be scary to grown-up liberals, abstract concepts make poor Happy Meal toys—but nothing in the way of compelling character development either. Everyone shows up to reprise their roles, because sequels of any kind are basically about more of the same.

Fortunately, that also includes Scrat, a bundle of pure neurotic survival drive thwarted by the natural world at every possible turn. Director Carlos Saldanha—who also directed the Oscar-nominated Scrat short Going Nutty—crafts a few moments of pure genius, nowhere better than when a cut out circle of lake ice repeatedly separates Scrat from his “prey.” Watching those sequences isn’t just enough to make you blow soda out your nose—it’s a reminder of what animated filmmaking could be if those who created them would stop pandering to crude humor or what they think we expect from a sequel. It’s time to put Manny, Sid and Diego out to the pasture of natural selection and allow the Ice Age team to focus on Scrat. To do otherwise would be just plain nuts.

ICE AGE: THE MELTDOWN

**.5

Voices of Ray Romano, John Leguizamo, Denis Leary.

Directed by Carlos Saldanha

Rated PG.