In Murphy's Lard, he was shown in a flashback with his son and his wife on a boating trip where Zack got scared by a fish that landed on their boat.
In Time Out he, Zack, Milo and Milo's dad to go on a fishing trip on Murphy's Yaw. At first, he doesn't believe in Murphy's Law, but throughout the day he eventually believes in the Murphy family curse.
In Milo Murphy's Halloween Scream-a-Torium!, his son revealed that he has scared the boy every Halloween, much to Zack's amusement. His most recent attempt had him dressed as a fish, his son's worst fear.
In A Christmas Peril he and his wife go to a Chinese restaurant at the mall with the Murphys, the Chases, Mort and Amanda.
He has dark skin and brown hair and a goatee. He wears a blue cap, a short-sleeved blue shirt, and beige shorts with brown sandals.
He seems to be easy going and calm under pressure, as shown during his and Zack's fishing trip with Martin and Milo.
The image gallery for Marcus Underwood may be viewed here.