From the Super Mario Wiki
Object D'Art is one of Kat and Ana’s Microgames in WarioWare: Smooth Moves. The term "object d'art" is French, meaning "object of art", but is often used in English to refer to something that is a work of art that is small in size.
The player must throw the dart anywhere on the dartboard. Getting a bullseye results in the dartboard being lit up.