He's the centrepiece of the movie's poster. He's the creature the kids are all waiting to see. And he steals the show with every fleeting moment he's on screen.

The cheery animated sequel Ice Age: The Meltdown might as well come with another subtitle: Featuring Scrat! The little part-squirrel, part-rodent thing is the Fonzie of this franchise, the supporting player who upstages the top-billed talent with his manic antics to secure his precious acorn.

The movie is right on par with the 2002 original: Brisk, pleasant and loaded with slapstick that should keep young children giggling, though repetitive enough that parents at times may feel they're sitting through the first Ice Age all over again.

The vocal trio of the original - two-thirds droll and dour with Ray Romano and Denis Leary, one-third babbling whirlwind with John Leguizamo - is smartly enlivened through the saucy addition of Queen Latifah.

But it's those moments with Scrat - whose bleats, grunts, howls and yelps are voiced with inarticulate glee by Ice Age director Chris Wedge, an executive producer on the sequel - that are the most memorable, as they were in the original flick.

Scrat stars in the opening sequence, and at a screening packed with families of critics and studio employees, his appearance was greeted with laughter and applause from kids and their parents. When the hapless Scrat and his elusive acorn popped up periodically in interludes between the main action, the audience buzzed with glee.

As the title suggests, endless winter is coming to a close for the prehistoric posse of talking animals. Best pals Manny the mammoth (Romano), Diego the sabre-toothed tiger (Leary) and Sid the sloth (Leguizamo) discover a giant ice dam holding back the sea is melting and about to break in a deluge that will flood the valley they co-inhabit along with a peaceable kingdom of turtles, birds and other gabby wildlife.

So the gang packs up and starts a long migration to safety at the other end of the valley. The lonely Manny, half-convinced he's the last of his kind since no other mammoths have been sighted in ages, is thrilled when he runs across spunky female mammoth Ellie (Latifah).

The only trouble is that Ellie, orphaned as a child, was raised by possums and thinks she's one of the little critters herself. Ellie and her mischievous possum brothers (Seann William Scott and Josh Peck) join the march to the far end of the valley, setting up a bickering romantic duo as Manny tries to convince her they're the same species.

Even more so than the first movie, the sequel written by Peter Gaulke, Gerry Swallow and Jim Hecht comes off as a series of comic episodes strung together along a loose central story.

Some sequences, such as Sid's detour to a land of mini-sloths that worship him, feel so disconnected they're like stand-alone short cartoons wedged into the movie to pad it out.

The computer animation overseen by Carlos Saldanha, who graduates from co-director on the original Ice Age and last year's Robots to full director here, shows marked improvement over the rather featureless glacial backdrops of the original.

Advances in digital technology allow the animators to create more detailed landscapes and expressive characters, though the imagery remains several steps down from the computer-animation leaders, DreamWorks (the Shrek movies) and Pixar (Finding Nemo, The Incredibles).

But the great asset Ice Age has that no one else does is good old Scrat. Unlike Fonzie, who progressed from bit player on Happy Days to cultural phenomenon of the '70s, Scrat could never carry the whole show.

In fits and starts, though, the fanged little goof asserts himself as the heart and soul of the Ice Age tales, adding warmth and loony pathos to what otherwise would be only a sturdy but temperate franchise.

Two and a half stars out of four.