From the Super Mario Wiki
Not to be confused with Baby Wario.
“If a spell is cast on me, I become tiny. I can't do anything when I'm tiny except run away.”
In Wario Land II, Wario could not be defeated by any enemy. Instead, some of the foes triggered transformations. Tiny Wario was among these alterations. The status effect can only be caused by a Wizard. With a shake of its wand, the Wizard turns Wario tiny. In this state, Wario cannot attack any enemies, but he is able to leap higher. The physical condition could be reversed if Wario falls into water or gets hit by an enemy. Also, the Wario Land II transformation is similar to the eventual Mini Mario form introduced in New Super Mario Bros.
In Wario Land: Shake It!, a form of Wario called Mini Wario appears but unlike Tiny Wario it is just a smaller version of normal Wario with no physical changes whatsoever.
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