Brock Mason is an X Middle School student. Fillmore thought he make had stolen X's mascot, Lobby the Lobster. It turns out Brock stolen Gibbe's goat mascot. He realizes that someone had stolen Lobby the Lobster and reveal it to the entire school. In the end, Gibbe's mascot is returned to it's school and Brock ended up on hoof-clipping duty though spring.
He is voiced by Brady Kimball.