Sonata is a white mouse. She has the normal characteristics of a "lab mouse", being all white with pink eyes, tails, and feet. It was her coloring that actually made her stand out from the other mice that inhabit the catacombs Operetta and her father call home. Operetta often puts a lavender bow on her head as well.
"...a little white mouse named Sonata. She’s so cute, and clean. Not how you’d expect a rodent to be."
- A "sonata" in music, literally means a piece played as opposed to a cantata, a piece sung.
- Operetta was given a mouse for a pet due to her living in catacombs/under an opera house where mice and rats often dwell.
- A humanized version of Sonata has her appearing as an albino girl in a very poofy dress in colors of purple, lavendar, and silver. She also still has her bow.