Bob Turtle is Joe Turtle's brother, or sometimes cousin. He is a police officer in Rainbow Valley, second to Chief Butthole (see: "Joonsul").
In the late era of the timeline, Bob Turtle becomes Dr. Diabolical, helming the evil schemes to obtain the diamond from Willy Sketch. He becomes a massive giant monster, who it is revealed has been letting the bad guys live inside of his shell.
Officer Bobby's egg got radioactive goo or mutagen spilled on it.
In Willy's Awesome Adventure, he appears in cop garb as always. He drives the Turtle 360 walker and commands the Bomblings to help Joe Turtle in capturing the good guys.
Later, when the Willys are presumed dead, he and Joe take over Rainbow Plateau, calling it Turtle Topia and ruling the low elves there. He dies in the destruction of their castle at the hands of Willy Johnson.