Boo is introduced as a character in the video game Super Mario 3D World, developed by Nintendo.
Boo first appears as a ghost enemy character in the game Super Mario Bros. 3, marking its debut in the Mario franchise.
Boo's design is refined in subsequent Mario games, solidifying its iconic ghostly appearance with a mischievous smile and shy behavior towards Mario.
Boo receives a more dynamic role as a playable character and unique enemy in Super Mario 3D World, showcasing enhanced gameplay mechanics.