Stewie's 1. His birthday is 18th April 1999. He celebrated his first birthday in the episode 'Chitty Chitty Death Bang' (Season 1). He remains the same age and a joke is made about this in the episode 'Road To Rupert' (Season 6) when Brian says: "Aren't you getting a little old to have a teddy bear?", Stewie replies: "Brian, I'm one." Brian then asks: "Still?"