Ashlee Simpson-Wentz and Pete Wentz party with son

Ashlee Simpson-Wentz and Pete Wentz threw their son a "rad" first birthday party on Saturday (21.11.09).

Bronx Mowgli – who actually turned one on Friday (20.11.09) – was treated to a 'SpongeBob SquarePants'-themed bash at his grandparents Joe and Tina Simpson's house in Encino, California, which even included an impersonator dressed as the goofy, yellow sea sponge.

Pete thanked his friends and family on Twitter for a "rad b-day for Bronx. (sic)"

The tot was joined by 30 family and friends – including his pop star aunt Jessica Simpson – who tucked into birthday cake and played on a giant bouncy castle.

Last week, Pete revealed his plans behind opting for the cartoon theme.

He said: "Bronx likes Bob and he likes guitar – which he calls 'itar' so we're going to have a SpongeBob party for him."

Pete was not Bronx's only family member to talk about his birthday celebration on Twitter.

Ashlee wrote: "BX's 1st bday tomorrow! My angel is going to be a year!! The greatest year of my life :) (sic)"

Jessica added: "Happy Birthday to my precious angel on earth!!! Bronx is 1 today!! I LOVE HIM SO MUCH!!! I can't believe it has been a year already. (sic)"