Opposite World is a location in Mario's Early Years! Preschool Fun. It is one of the six islands in the game and is represented by the two stereotypical theatre masks (Comedy and Tragedy.)
In this world, the player has to select the set of opposites specified. The first level involves selecting the opposites of certain attributes (Cold, wet, empty, least, soft) of various fast foods/drinks. The second level involves choosing opposites of various spatial directions (Bottom, Under, Off, Down.) The third involves judging the opposite attributes of various animals. (End of a line, Smallest, Front/Back of a line, Tallest) After the player selects the correct answer, a character will pop up to encourage them, then after 5 correct answers they will move on to the next room via a pipe.
The first area is the concession stand of a circus, with the platforms being vendor carts. The second area is a green merry-go-round where children are seen riding. The third area is the room of a pet judging competition; the player exits through a blue pipe in this room.