The computer animation may be lovely — hair is soft and realistic, fire is gorgeous — but that can’t make up for a humdrum script that steamrollers the audience with an overly sentimental story we’ve seen too many times before. As glaciers advance, a woolly mammoth, a sloth, and a sabretooth tiger team up to help a lost human child find his way back to his tribe. The whole lion-lying-down-with-the-lamb (or tiger-with-the-sloth) thing is preposterous enough, as is one of the central jokes — animals can talk and humans can’t — but the real offense here is the watering down of what should be a grim Grimm lost-in-the-woods fairy tale. Sure, it’s safe for kids… too safe. Fear goes hand in hand with enchantment, and there’s nothing here to stir the soul of a child — the peril has been blandified, the genuine terrors of childhood (like the loss of a mother) whitewashed in favor of cutesy animal schtick. What could have been a new Bambi or Dumbo is instead an advertisement for a yet-to-be-built theme-park ride. All that makes this worth an eventual video rental is the concurrent adventures of the Scrat — part squirrel, part rat — and his attempts to bury his acorn in solid ice. It’s got nothing whatsoever to do with the baby story, and so it’s wildly inventive and hysterically hilarious, like an old Warner Bros. cartoon we’ve never seen before — the Scrat is a prehistoric Wile E. Coyote. Ice Age should have been a short about him.