Kokko-chan is a fairly obscure character in the Sanrio menagerie, and not much is known about her background. I can share the following:

She is a fun-loving chicken, and has a younger brother, named Hiyoko-kun, with whom she goes everywhere. She keeps her mind sharp with puns and keeps a tidy nest. She has a tendency to become overweight. She was born in the year 1992. Due to her obscurity, she is quite collectable, especially in the context of food, such as egg cups and cutlery.