His short life was bookended by sad circumstances. But in between, Knut, who died March 19 at 4, became one of the world's most famous animals. A seemingly never-ending stream of images of the polar-bear cub--initially abandoned by his mother and hand-reared by zookeepers--helped turn him into a media darling who would eventually appear on the cover of Vanity Fair. At the Berlin Zoo, hundreds of thousands came to watch Knut as he grew into a full-size animal. Indeed, the area around his tank was crowded at the moment he died, collapsing suddenly into a pool of water. While the cause of death wasn't immediately clear (a necropsy suggested he suffered from brain damage), by all measures Knut died young. He should have lived for at least another decade. Within a day, mourners had begun to flock to his tank.