Gumball (formerly Zach) Tristopher Watterson is the main character of The Amazing World of Gumball. He is a thirteen-year-old, light blue male cat that goes to Elmore Junior High, with his ten-year-old adopted brother and best friend Darwin, and his four-year-old sister Anais. Gumball is in Miss Simian's class. As of "The Shell," Gumball is dating Penny.

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. He usually wears grey trousers, coupled with a tan sweater, which has brown cuffs and a brown collar. 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.