On Friday, his actual birthday, he was serenaded by fans at the Berlin zoo as he demolished a birthday treat of fish and vegetables.
Judy Lydecker, 62, a social worker from Winsted, and a member of a Knut fan club called the "Wild Herd," said she flew in for the occasion.
"It's hard for me to put my feelings for Knut into words," she said. "We have a very strong connection. I was here for his birthday last year, too."
Knut was hand-raised after his mother rejected him at birth. He rose to stardom early last year as an irresistibly cute white ball of fluff, but has grown rapidly since.
Friday, a crowd of about 200 erupted into "oohs" and "aahs" and sang "Happy Birthday" as Knut -- sporting a shaggy, brownish coat -- lumbered out into his enclosure.
The bear tore into his birthday present from keepers, a cloth bag bearing his name and the number 2 that was full of fish and a birthday cake of frozen vegetables. Then he turned his back on the crowd and slunk off toward some rocks.
Friday's celebration comes amid uncertainty over Knut's future in Berlin. Zoo officials say he will have to move if they do not build a new enclosure, which appears virtually impossible due to lack of space.