Minni is the main character of Howmonica.
Minni has a white head with light pink cheeks and two black, rectangular eyes. Two "antennae" poke out from her head, with white squares at the top of them. Her body is several different shades of pink. She resembles the appearance of a cupcake with two ears.
The player uses Minni, in all levels of Howmonica, to fulfill the goal of colouring all blocks within a level. When Minni touches a block, it turns purple, indicating that she has made contact. To reach all the blocks, Minni is able to flip when on a block as well as in mid-air to reach areas otherwise inaccessible by horizontal movement. Any hit from spikes forces the player to restart the level they were on.
Although no other character information about Minni is revealed in-game, the author comments on the Howmonica page on Newgrounds refer to Minni as a "Cupcake Color Bunny on an adventure to colour every block in the world".