Gumball Watterson is a 12-year-old blue cat who goes to Elmore College with his adoptive brother, Darwin, and his four-year-old sister, Anaïs. He is a student in Miss Simian's class. Gumball and Penny are together. Gumball is a very childish person also full of imagination. Despite his poor academic performance, he can be surprisingly brilliant when it comes to developing all kinds of mischievous projects. Gumball is rather optimistic. Despite his cynicism towards society, he often expects others to act positively. In general, Gumball is very protective of his loved ones, especially Darwin and Anaïs. He often makes mischievous remarks, ranging from relatively harmless to extremely brutal and rude. This kind of comment seems to be impulsive, and sometimes he can't do anything about it. Gumball could do absolutely anything for Penny. When he believes that Leslie wants to steal her from him as a girlfriend, he releases in him an insurmountable jealousy that pushes him to do horrors.

Darwin Watterson, is Gumball's adoptive brother and best friend. He is an orange fish. Arms and long legs hang from the big head that serves as his body. He still kept his caudal fin and uses his pectoral fins as an arm. He often wears green and white sneakers, has oval eyes with black pupils, like Gumball, except that he has three eyelashes compared to Gumball who has none. Darwin is a cheerful and optimistic person, who always tries to take life on the bright side. He is not only content to be happy, but also seeks to please others. He always expects the best from others and has a somewhat naive and idealised vision of the world. Darwin also has a deep sense of honesty. Above all, he wants to be sincere, no matter what it may generate. He is very attached to his moral principles, and he is often the first to prevent his brother from committing wrongdoing. He avoids resorting to dubious solutions, preferring first the honest approach, which is often the simplest. This trait makes Gumball see him as a moral guide. Darwin also shows great sensitivity. He is very affectionate with his family and more particularly with Gumball. So much attachment is sometimes a source of weakness, since he tends to become possessive when he feels distant from his loved ones. However, despite his natural joie de vivre and optimism, he sometimes gets angry. Although it is rare for this side of him to arise, Darwin can resort to violence when he is pushed to the limit. He obviously can't make decisions at all. It is very easy to manipulate. If he is faced with a decision and no one assists him, Darwin gets lost in his head.

Anaïs Watterson is the youngest, but also the smartest of the Watterson family. Despite being four years old, she goes to Elmore College with her older brothers, Gumball and Darwin, and is even a year ahead of them. Anaïs is a little pink rabbit with a white tail. She looks like her father, Richard, but she is much smaller than him. Her nose is red, like Gumball's. She usually wears an orange dress with a white collar and white socks. She is one of the only members of her family who is not barefoot, with Darwin. Anaïs is by far the smartest in her family. She has a very high IQ. She is part of the college physics club. Anaïs is also an incredibly cunning strategist. Despite her great maturity, Anaïs sometimes has more typical behaviours of a child, appropriate to her age. She is a fan of Daisy the little donkey, judging by her enthusiasm at the idea of seeing her at a figure skating show. She has a Daisy plush, which she cares a lot about. She also believes that kissing frogs will make her prince charming appear. Anaïs sometimes shows a temperament similar to that of her mother.

Richard Buckley Watterson is the father of Gumball, Darwin and Anaïs. He is a very bad example for his children. Despite his misguided advice and his unrefined side, Richard is well-intentioned and is very loving towards his family. Richard is a family man, but has no sense of responsibility and rarely shows common sense. He is very immature, childish and lazy, and also does not show a good example for his children. He is also very good at avoiding chores. Despite this, he still has good intentions towards his family.

Nicole Watterson is the modelle mother of the Watterson family, and the most responsible of the family. She is very devoted to her family, and does everything in her power to make them comfortable and safe. Unfortunately, because of her many responsibilities, Nicole suffers from enormous stress. She is often strict and demanding, and it is better not to provoke her. Once, Gumball even notices that he prefers to face a T. Rex rather than Nicole angry. When she is pushed to the limit, she becomes a real monster.

Penny Fitzgerald is a shapeshifting fairy student in Elmore College and Gumball's girlfriend. She is an anthropomorphic peanut. Just like the rest of her family, a pair of wood comes out of the top of his head. Penny is a loveable girl. She does not hesitate to defend her friends and shows a great sense of integrity and she is one of the few people to understand Gumball.