Monophanie is a child-like robot with a feminine personality. Her personality appears much more gentle than her brothers, and her kindness is mentioned to be "a unique character trait", which seems to make her somewhat well-liked by her father and siblings, though it can also annoy the other bears who are more openly "evil". She isn't good with gore and cruelness, which is why she is very often seen vomiting, with the vomit even turning different colors depending on the situation. According to Monotaro, her green puke is an omen of bad luck and disaster, and anyone who sees her blue puke will have good luck.

Voice reference: https://www.youtube.com/watch?v=9BQtOLhVhXo