Billie is a female mouse, another result of gene splicing. She is smarter than Brain, and makes him afraid she will beat him to his goal of world domination. He loves her: she fancies Pinky. Despite Billie having great intelligence, she can act a bit ditzy at times. Billie first appeared on Animaniacs in the short "The World Can Wait"
Billie Who is not a Bunny-Mice Hybrid.
Season 03, Episode 03 "Brain Noir"
Season 03, Episode 30 "You'll Never Eat Food Pellets in This Town, Again!"
- In You'll Never Eat Food Pellets in This Town, Again! Brain is married to Billie but her real name is Sheila and that she complains not being in more of the show.
- Also she said that Billie only appeared in 3 episodes but she only appeared in 2. However She could have been referring to her Debut in Animanics.
- Billie's real name is Sheila.