Gilbert is an anthropomorphic dog.
Gilbert is Goofy's nephew who often stays at his loopy uncle's house. Unlike most members of the Goofy family, Gilbert is a precocious genius who already graduated from university as a young teenager and often cooks up inventions (though his is a more "grounded" sort of science than Gyro Gearloose's). Gilbert often tries to save Goofy from the consequences of his biggest goofs, and that includes relentlessly assisting his uncle in the guise of Super Goof (sometimes becoming a goober-enabled superhero himself as Super Gilbert). He might be the brother of Debbie.
Behind the scenes
Gilbert first appeared in the 1954 story Relative Genius.