Maskutchi is an adult Tamagotchi who's been around since the original Tamagotchi released in Japan. The character goes by a few name variations—Masktchi and Mask-tchi show up in early materials—but Maskutchi is the standard.
Visually, it's pretty distinctive. The character has a round, white bean-shaped body with stubby violet ears sticking up on top, two thin stick legs, and wears a matching violet mask. Early Japanese artwork actually rendered those violet parts as indigo instead. The US version went a different direction entirely—blue body, black ears, and a black mask.
Content compiled by AnimeList.moe from publicly available sources.