Memphis accidentally lets his un-hatched egg roll off into the snow. He panics and scrambles to get it, scooping it back up on his feet and under his belly. Later, when all of the other chicks are hatching, Memphis is worried that his hasn't, and he and others think that it might contain a dead chick (but young Gloria starts tapping on it, resulting in Mumble finally hatching).
Some large birds surround young Mumble, with the obvious intent of eating him. The leader pins Mumble to the ground with his foot, but Mumble manages to distract him (by making the bird tell a story) and then back away. Mumble then falls backwards and lands in a hole or small cave, just out of the reach of the birds' sharp beaks that they thrust down into the hole at him. They then fly off.
Mumble fights with several birds that have grabbed the fish he had caught for Gloria. They end up flying him high into the sky, where he eventually breaks free and falls a long distance to the hard, snowy ground below. He's motionless and younger kids may worry he's dead, but he's just dazed and later is okay.
Mumble ends up on a tiny chunk of ice that moves from beneath, and then does so again. We then see an underwater view where a leopard seal swims by in the foreground, followed by it trying to catch and eat Mumble (with its open mouth and very sharp teeth coming right at him). A chase ensues underwater through an icy structure, with the seal getting Mumble by his tail feathers, but the smaller penguin manages to escape, popping up to the surface where he now has the mobility advantage over the lumbering seal. Nevertheless, the seal slowly comes at him, occasionally lunging, but Mumble (who's joined by Ramon and his pals) simply move out of the way while repeatedly taunting the seal.
While sliding down an icy slope, Mumble, Ramon and the others accidentally slam into each other, icy structures and such (all for fun), but they end up causing an avalanche of sorts that they must avoid after falling into a body of water. A large tractor sinks toward Mumble and he must avoid it, just like two large pieces of ice that slam together quite close to him.
Two killer whales come after Mumble, Ramon and the others who are now on a buoy on a small chunk of ice. One says they'll be okay if they don't get in the water, but the whale tips over the buoy, spilling all of them into the sea. Lovelace gets stuck on a heavy bell that then sinks and draws him down into the depths, with Mumble racing down to try to save him. But the whales get there first, and rather than eat them right away, they decide to play with them, thus tossing or flipping them back out of the water. One then swallows Lovelace, but spits him back out as they continue to "play" with them in a rough fashion. They continue doing that and chasing them, but then swim off when the penguins end up back on solid ice, only to have an ice breaker ship come right at them, tossing them about in the chunks of ice it creates.
As Mumble holds onto a closed fishing net pulling up a catch to its ship, a hook grabs and yanks Mumble off it, with him falling back into the sea where he barely avoids being pulled into the ship's huge propeller. Mumble then continues to pursue the ship, but we later see him washed up on a shore (younger kids may think he's dead, but he's just unconscious or sleeping).