When Mom and Dad struggle to keep hyperactive, toddler-aged Gumball from trashing the house and exhausting them, they decide to buy him a pet. It works, but there’s a problem: every goldfish they get him is short-lived, and inevitably ends up being flushed down the toilet. However, when Dad buys a talking goldfish from a mysterious shop, Gumball meets the best friend he’ll ever have. Having been accidentally flushed down the toilet, Darwin has to find his way back to his new family.
Via the sewers, Darwin finds himself flushed out to sea. He is terrified, but determined to make his way back to the Wattersons. However, a fish can’t get very far on land, so Darwin will have to do millions of years of evolution in a matter of hours if he’s going to get home safe and sound.