Mustard Cookie is a very contrarian Cookie. She hates assumptions about her based on her appearance, as well as the assumption that Cookies have to be sweet. She accuses others of bias, and seems to really only have respect for other artists or people she considers "different." her grades suffer due to her focus on art. She has a very low tolerance for Dr. Wasabi Cookie and her antics, but still seems to care deeply for her, enough to follow around behind her cleaning up any potential mayhem.