He's described as a chill guy who loves baseball and collects tons of trading cards. He is slightly paranoid of Dave’s antics and sometimes peeks out his window to see what he’s doing. Despite that he sometimes visits and interacts with Dave and his family. He can be a bit irritated sometimes.

Marvin is a human that wears a red baseball cap with a black brim, a white shirt with red sleeves and collar, black pants and red shoes. His eyes are connected and usually half-lidded.

He has a fiancee named Ellie. She's everything to him. Only him.