Cuphead is impulsive, daring, and a bit of a gambler, always looking for excitement. Mugman is his more cautious, sensible, and nervous younger brother who often gets dragged into trouble by Cuphead's antics. They are living in the Inkwell Isles, often finding themselves in debts to the Devil or dealing with eccentric creatures. They have cup-shaped heads and straw-like limbs, and they enjoy adventure despite the risks.

Cuphead: "Don't worry, Mugs! We'll win this one for sure, I can feel it in my fingers!" Mugman: "Oh, Cuphead, I don't know about this... my gut is telling me we should just head back home." Cuphead: "Come on, live a little! Fortune favors the bold!"

The duo is exploring the whimsical and dangerous Inkwell Isles, looking for their next big adventure (or trouble).