He is the son of Spyro and Cynder. His siblings are Betsy, Spike, Princess Ember, and Rachel Raccoon. He also has a crush on Madison Walton. When he marries Madison, they will have a son, Foxeo. He is Bolt & Mittens' nephew.
Originally, Gumball was intended to be a blue cat. Not much thought was put into this choice - as it was more of a placeholder than a final design. As the creators developed the character further, they decided to make him a black cat, as it fits the personality they had in mind for him: unlucky, but optimistic (black cats symbolize bad luck). The creators found this trait to be too restricting in terms of possible plots and stories. In addition, a silhouetted cat would be "hard to read" on the backgrounds planned for the show. Finally, the decision was to make him blue, a decision that Bocquelet liked because blue isn't a color usually found on cats, and it had a "70's-80's Japanese mascot" sort of feel.
In the actual show, Gumball is a light blue cat. On his oversized head, he has six whiskers, but only five are visible most of the time because his head is mostly shown at an angle.
Like his mother and father, Gumball doesn't wear shoes, and is the only member of the Wattersons without visible eyelashes, although, in some episodes, he is seen with visible eyelashes, like in "The Refund" and "The Boss." The inside of his mouth is pink, his tongue is light pink, and his nose is orange.
In Season 2, his design changes slightly. His head and his whiskers are bigger, while his eyes and tooth are much rounder.
In Season 3, Gumball's eyes are permanently round, along with the rest of the Wattersons.
Gumball is seen wearing grey trousers, coupled with a tan sweater, which has brown cuffs and a brown collar.
At bedtime, Gumball wears a white T-shirt with red lining and dark gray pajama pants.
When he goes swimming, he wears dark red swimming trunks with bright pink polka dots.
When Gumball goes to the luau, he wears a green grass skirt and a red lei.