Stewie is the temporary sidekick of Joe Balooka.
His first appearance was in Operation: S.P.A.N.K.E.N.S.T.I.N.E. and his only line was, "But's it's dark in there, Joey!" He was asked to check inside Joe's dad's store for the money Numbuh 2 claimed to have left for the chocolate sauce. Joe then yelled at him, which sent him running inside.
Shortly after disappearing, he was brought back outside and spanked by the Spankenstine Monster and then thrown away. He was not seen again until the end when he and Joe went to Numbuh 3's house to apologize for accusing Numbuh 2 of stealing. He is a skinny boy with black hair.
- He is afaid of the dark
- He has cameo appearances in Operation: L.U.N.C.H. and Operation: S.N.O.W.I.N.G.