She appears to be friends with a female snake (whose name could possibly be Gina). She enjoys watching the fish in the tanks, and is a little more short-tempered than the snake. Starting from the first episode, Mouse and Snake always appeared in the end credits, usually talking about what the episode is about such as pets, adulthood, football, or humor. She thinks that clowns are funny.
- She is a mouse that does not seem to be afraid of Snake.
- She enjoys watching the fish and the other pets ("Bea Stays in the Picture", "Fish Out of Water").
- She thinks that clowns are funny ("Fail Fish", "Funny Fish").
- Mouse wants to have a late night talk show ("Hooray for Hamsterwood", "The Tale of Sir Oscar Fish").
- She plays the flute.
- Mouse is a talented singer.
- She thinks Snake is weird.
- Mouse ate an entire jar of mayo once.
- She doesn't mind spring cleaning.
- Her brain is like Albert Glass's brain.
- Mouse thinks dancing is for spiders.
- She doesn't go to school dances because she gets smeared on the glass on the tank.
- Mouse likes to hit things.
- Mouse and Snake used to have a band.
- She thinks curfews are dumb.
She has appeared in all of the credits (except for "Fish School Musical") so far, had a cameo at the beginning of "Hooray for Hamsterwood" when she jumped over Bud with a motorcycle, made a cameo at the cheer-off in "We've Got Fish Spirit", and made a cameo with Snake in "Halloween Haul".