Wario is Mario's evil counterpart in the Nintendo Mario games.
He first appeared in Super Mario Land 2 as the antagonist who stole Mario's castle. Then, Wario started appearing in his own series of games which include:
Wario also appears as a secondary character in Mario games such as:
The name "Wario" can be taken to be a blending of Mario's own name with the Japanese adjective warui meaning "bad"; hence, a "bad Mario".