He is a normal green Frog, until Mortimer's ending where he became exposed to radiation, he became ten times bigger.
In the intro to Small Brawl, Goulber was with Mortimer on a hill, where Mortimer wanted him to jump to him, until he noticed Billy Calypso, who punched Mortimer in the face, and snatched Goulber from under him. Billy told Mortimer, to in order get Goulber back, Mortimer had to play Billy's game.
In Mortimer's ending, Billy was annoyed by Goulber's croaking that Billy couldn't go inside his hangout. Mortimer told Billy that Goulber's croaking was caused by radiation, and told Billy that he can "keep" Goulber, and ran off shouting "Victory!" before Goulber ate Billy whole.
- Goulber is the only known animal to be named, by at least one of the characters.
- It's unknown how or why Goulber was exposed to radiation, though it was probably because of Mortimer's interest in science.