Mr. Gus is slightly taller than Uncle Grandpa, has a slightly overweight yet "built" appearance, having a body that's halfway between a tyrannosaurus rex and Godzilla. Though he's often referred to as a dinosaur, he can also breathe fire and remove his head - though these bits can easily be attributed to the magical powers of Uncle Grandpa and the UGRV. His body is green, his eyes are yellow, and he's always wearing a muscle shirt.
Mr. Gus generally acts unenthusiastic about his situation, though on several occasions he expresses his satisfaction having friends and a place to live his life in peace. He enjoys watching tv, acting, reading, and lifting weights shaped like the Empire State Building while being shot at by mini helicopters and tanks.
Mr Gus is friends with Uncle Grandpa, Belly Bag, Pizza Steve, and Giant Realistic Flying Tiger. Mr. Gus has been on the planet Earth for tens of millions of years, having been born before the extinction of the dinosaurs.