Muffy is a black sheep with purple striped horns. She has wide, bright cyan eyes with large black pupils and noticeable eyelashes. She appears to be wearing pink blush and black lipstick. She initially wears the Natty Shirt as a scarf, as sheep wear their clothes as scarves, and carries a Zebra Umbrella when it rains. In New Horizons she initially wears a purple Ruffled dress.

Her look may be inspired by the gothic lolita fashion subculture. The rectangle headdress she wears is iconic.