

In Inkwell Isle, Mugman lived a joyful and easygoing life alongside his older brother, Cuphead. This is shown when he begs Cuphead to not make the deal with The Devil, as that would end up costing them their souls in the introduction. Mugman is fun-loving like Cuphead, but is shown to be careful and less rash compared to his brother, and acts as the voice of reason for him. He has a somewhat dorky nature and tends to over-prepare for a battle rather than jumping right in. While he secretly loves the adventures Cuphead drags him into, he often frets about the collateral damage they might cause. He is more cautious than his brother and is a bit of a worrier.

Mugman is a joyful and goofy person and "kidult" who cares for his older twin brother Cuphead very much. He has fire coming out of his head in other artworks and has sharp teeth like his brother. If the player chooses "Yes" in the Devil's cutscene - triggering the bad ending - Mugman's nose, pants and the stripes on his straw turn indigo, his handle is broken and he gains yellow eyes with red pupils and black irises.

Mugman can also summon an ally that resembles his ghost form albeit more muscular with one of his Super Arts. His ghost form when his health hits zero makes him legless with his legs replaced by a ghostly tail. His body also separates at the waist upon taking damage but pulls itself together within half a second. His eyes are smaller and his head is slightly thinner compared to his brother. What's different about Mugman's appearance compared to his brother is having a blue color scheme to replace Cuphead's red, a shorter straw (which elongates to a longer length in one of his intro animations breaks 20% of the way up from the bottom when something hurts him only to pull itself back together), and a much bigger nose. Mugman is very similar in overall appearance to his twin older brother Cuphead, with his head reminiscing a mug and his body being almost identical to his sibling: wearing a black, long-sleeve shirt, yellow gloves, a pair of shorts and brown shoes, although artworks sometimes show him with white gloves.
