Mr. Grumpfish is an adult fish formerly known for never liking anything. His actions changed when he visited the Picture Pizza Parlor and was served the special: a pizza with his face on it. He thought that the joke was funny and laughed and was known as a happy customer. He also, much to everyone's surprise, does not like the Holidays. But, after visiting Mayor Grouper, the Guppies figure out he loves gingerbread. The Bubble Guppies happily decorate his house to look like a giant gingerbread house making him smile, laugh, and enjoy the Holidays.
Grumpfish is mostly gray-green, and as large as Mr.Grouper. He has two eyes and one mouth.