Ice Age 3

Buck rallies the troops in Ice Age 3: Dawn of the Dinosaurs, but the novelty of the franchise is close to extinction.

Fox Animation may be languishing well behind DreamWorks, Aardman, Disney and Pixar as far as brand recognition goes, but the popular Ice Age franchise and last year's hit, Horton Hears a Who!, suggests that the studio is doing something right.

Subtitled Dawn of the Dinosaurs (nonsensically: it's set after their supposed extinction), Ice Age 3 is strictly surplus to all natural storytelling requirements. Make no mistake: it only exists because the accountants demanded it. But every studio needs to exploit its cash cows and it takes real craftsmanship, if not artistry, to do it so well. In 2002, the first Ice Age movie was a kind of anthropomorphised Three Men and a Baby, although you could trace its roots further back, to the John Ford/John Wayne western Three Godfathers (itself a remake of a silent picture from 1916) in which a trio of bankrobbers accidentally inherits an infant. In the animated version, a sloth (Sid), a woolly mammoth (Manny) and a sabre-tooth tiger (Diego) are thrown together by circumstance and the discovery of a mewling human baby. Putting aside their differences (and Diego's natural inclination to eat the kid), they embarked on a risky journey to restore him to his people.

Come 2006's Ice Age: The Meltdown: Manny meets a mate, Ellie, who is under the mistaken impression that she is a possum and the strange herd saves the entire valley from a potentially devastating flood. In Dawn of the Dinosaurs, Ellie is with child, Manny is thoroughly domesticated, Diego is hearing the call of the wild, and klutzy and addlebrained Sid is feeling broody - so much so that when he happens across three seemingly abandoned eggs, he adopts them as his own. The babies that emerge all have big teeth and appetites to match, but Sid is not discouraged until an angry T-Rex comes to reclaim them and leads him down to a subterranean "lost valley" of the dinosaurs. Needless to say, Sid's pals decide they must follow.

After a lachrymose start that belabours the fissures threatening the friendship of the three males, Ice Age 3 soon reverts to the frantic pace of its predecessors. Underground (a much more verdant environment than you might expect), Sid and his friends face one perilous adventure after another. With their breathless concentration on high-stakes action - intermingled with a few choice wisecracks - these movies are really a throwback to the Looney Tunes shorts that came out of Warner Bros in the 1940s and 1950s: it's safe to say that Wile E Coyote and Roadrunner would be up to speed in this company.

The franchise even has its own supporting short in the shape of a running gag about a mute squirrel, Scrat, and his fruitless attempts to hold on to an elusive acorn. In this instalment, his struggles are complicated by the arrival of a female squirrel, who is both a rival for the nut and a distraction in her own right. Of course, the Looney Tunes shorts didn't have to sustain our interest for 94 minutes, and Ice Age: Dawn of the Dinosaurs struggles to find room to develop each of what is now a lengthy cast of characters. Diego (voiced by Denis Leary) and Manny (the Everybody Loves Raymond star Ray Romano) are left fighting over scraps in a script which doles out perfunctory character arcs like goody bags at a children's party: everyone gets one but they'll be landfill by morning.

Meanwhile, the irritatingly immature and idiotic Sid (the perennial supporting player John Leguizamo) gets the lion's share of the dramatic focus and the comedy bragging rights. More accurately, he splits most of the screen time with yet another character, a one-eyed weasel named Buck who serves as a guide to the land of the dinosaurs. Voiced by the British comedian Simon Pegg (Shaun of the Dead), Buck is a reckless adventurer likely modelled on Shrek 2's scene-stealing Puss in Boots.

Buck is an engagingly eccentric fellow - evidently out of his mind and often as not dead wrong in the leadership department. The filmmakers seem to be in two minds themselves about whether to keep him on hand for a potential third sequel, but the truth is that the next Ice Age needs less characters and more story. There is enough wit and technical acumen on display to keep part three moving along briskly, but take a step back and you can see the series is running on a treadmill. It can't go much faster before falling flat.