Stewie is the youngest of Peter and Lois Griffin's children that were former neighbors of Cleveland's in Quahog. He appears in the Pilot episode with his older siblings, Meg and Chris, at Cleveland's send-off. He is apparently angry and jealous that Cleveland got a spin-off and not him.
In "Ain't Nothin' But Mutton Bustin'", stuffed Brian and Stewie toys are available at the fair, The booth runner calls Stewie "Stevie", and one of the sayings the Stewie toy has is an admittance that he's gay, a reference to Stewie's sexual confusion.
Cleveland does his impression of Chris in "Your Show of Shows", asking Stewie to come smell his butt.
In "BFFs", Brian and Stewie distract Cleveland off-screen as they are still inside their house, while Peter sneaks to his car, not wanting to speak to Cleveland.
Stewie is seen as a balloon in the Stoolbend Thanksgiving parade in "Turkey Pot Die".