Scrat was a sabre-toothed squirrel. Twenty thousand years earlier, he completely filled an enormous wooden log with acorns. Those acorns were gone when he caused a continental drift, which was mysteriously reversed shortly thereafter.
Following that incident, he had acquired another acorn from that tree that he came across. He suffered through many unfortunate events trying to bury the acorn in various places. When he roasted it over an open fire, he ended up turning it into a snack that was ahead of his time. He ate what we call "popcorn" and nearly choked to death in the process. When he ran to the nearest body of water, he noticed a new acorn floating by. He had to follow it.
He pursued that acorn northward for a long time until it ended up being stuck in a glacier. The water terrified him, but he would do anything for that acorn. He swam in the ice-cold water. He was close. He nearly got a hold on it. However, he was frozen before he could do so. Frozen, but not dead.
20,000 years later, a block of ice containing Scrat and the acorn. It washed onto the shore of an island in Hawaii. The ice slowly melted. Scrat could not grab the nut. Over time, water trickled off the ice and onto the sand, ending up in the saltwater. When the ice only covered Scrat's bottom half, the acorn was free. The saltwater moved forward, and the acorn floated away. Scrat was stranded without the acorn.
He was furious. All those miles and years for that one acorn. He got into a rage and broke the ice.
"AAAAAHHHHHHH!"
He kept on screaming and yelling in frustration. He banged his head on a nearby tree a few times, causing a new nut to fall off. This nut was different. It was large and spherical. He could barely carry it. He joyfully buried the coconut in the sand until he heard a sound. He observed the ground and saw a crack appearing like it did on the ice all those years ago. The crack continued forming until it reached a volcano. It was errupting.
Scrat shrugged and held his hands up as if to say, "Here we go again!"