He is the polar bear who melted hearts around the world.
And now Knut has proved he is still a hot attraction after hundreds of people turned up to his birthday party.
Crowds sang 'happy birthday' as Knut, who has just turned two, lumbered out of his enclosure at the Berlin zoo.
According to a posting on his blog, Knut had planned to spend the entire day 'doing his favorite things' - a list which included playing with his ball and 'eating a lot.'
The bear tore into his birthday present from keepers, a cloth bag bearing his name and the number two, that was full of fish and a birthday cake of frozen vegetables.
He delivered a bravura performance for spectators in which he repeatedly stood on his hind legs and tossed his ball to the assembled throng.
Rejected by his mother at birth, Knut was subsequently raised by zookeepers, and has since been dubbed Germany's most famous orphan. He was the first polar bear cub to survive past infancy at the Berlin zoo in more than 30 years
It has credited Knut with a 27 per cent increase in visitors in 2007 and profits of nearly £6million from the products with his image, including stuffed animals, T-shirts, mugs and DVDs.
But his time at the zoo could be coming to an end. At nearly 450 pounds, Knut is outgrowing his enclosure, and zoo officials say they may have to relocate him so he can set up home with a fertile mate.
However there is no shortage of potential suitors who would be happy to offer him a new home.
The website Unibet is even running odds on the zoo likeliest to get the bear, with Zoom Erlebniswelt in Germany the favourite.