Miumiu is Professor Moshimo's young and beautiful assistant, as well as his fiancee. She can frequently be seen helping her fiance in his work although especially when she isn't trying to pull him away from it with her affection.
Despite the obviously vast age difference the couple, it's just as obvious than Miumi and Professor Moshimo genuinely love and care about each other—one example of such is when she continually pulled Moshimo away from a holo chat with Robotboy to make out with him.
She can for the mostly always be seen wearing a form fitting kimono. In Season 1 and 2 she's wearing a black colored kimono with red stripes while Season 3 and 4 it is changed to purple while keeping the same color for the stripes.
She's mostly known for being quiet almost all the time (except for two episodes where her voice can be heard.) It is unknown the reason why she is always silent, though she isn't voiceless, we can hear her giggle on Season 1 on the episode Brother. She doesn't speak clearly until Season 4 were she speaks in the episodes: "Grow-No-Mo!" and singing in "Cheezy Fun for Everyone".