Which episode of family guy has the part in where Stewie keeps going Mum Mummy?
The episode where Stewie says "Mum Mummy" repeatedly is
"The Courtship of Stewie Griffin" (Season 2, Episode 1).
It's a classic episode where Stewie falls for a young, attractive woman, leading to him saying "Mum Mummy" in a desperate and slightly disturbing attempt to woo her.