"SpongeBob" voice actors Bill Fagerbakke, left, and Tom Kenny in New York on June 24. Fagerbakke, 66, came aboard after Kenny was cast. “It was the most unusual audition I’ve ever had,” he says.

SpongeBob and his pals also showed up, including best friend Patrick, Squidward, Sandy Cheeks and Eugene H. Krabs. Pharrell's birthday cake was also appropriately in the shape of the Krabby Patty.

Though SpongeBob’s television debut came on May 1, 1999, the character’s previously established birthday was much earlier, and happens to be today! In the continuity of the series, as seen on ...