To use as prop - "(Tezuka's) wife is very quiet normally, but one day she exploded, maddened by all the time he spent at work. In the game, there is now a character who shrinks when Mario looks at it, but when Mario turns away, it will grow large and menacing." –Shigeru Miyamoto, on how co-creator Tekashi Tekuza inserted his wife into Super Mario 64; Nintendo Power

Super Mario Bros: 25 Mario facts for the 25th anniversary

Boo is playing with Mario while Luigi is watching them..

Aww poor luigi I can see Luigi playing with a boo more likely though. Luigi owns a mansion full of ghosts, and mario is scared of ghosts.

pumpkin carving boo mario - Google Search

Vinyl Decal Sticker - Big Boo Ghost decal inspired by Super mario Brothers for Windows, Cars, Laptops, Macbook etc