A blue mouse with yellow ears who wears an orange or pink ribbon on his tail. He is the closest among My Melody and My Harmony's pet mouse. Whenever there's trouble, especially a curse created by Kuromi's magic, My Harmony and My Melody sometimes cast a spell on Flat to deal with it. There have also been hints that Flat may have a crush on Marie and My Melody; for example, blushing when she hugs him in one episode.
Flat also has great social skills when it comes to interacting with the opposite gender. With these, he occasionally gives pointers to Kakeru when trying to contact Uta in certain situations.
