Super Mario Bros. 2/Subcon
Subcon (derived from Freud's 'subconsious') is the mysterious dream land in which the American version of Super Mario Bros. 2 (Super Mario USA in Japan) takes place. This land is inhabited by many denizens that have since become regulars in the Mario series, such as Shy Guys and Snifits. This game also introduces many game-exclusive bosses, such as Tryclyde, Fryguy, and most notably Wart.
Subcon is also the name of the pixie like inhabitants of this land, which have been captured by Wart. This land has never made an appearance since Super Mario Bros. 2, but several enemies appear in other games, such as Birdos, Ninjis, Bob-ombs and Pidgits. The last reference to Subcon was the Super Smash Bros. Melee stage Mushroom Kingdom II.