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From Unmariowiki

Yahoo! is a company in Earth. It also appears in the game Super Mario's Cupcakes, as the boss of the 4th world. Its weak point, just like Google, was it's 2 O's. It attacked by throwing its Exlamation point at mario like a boomerang. Also, the Y would shoot lazer beams at Mario. Yahoo! made a cameo appearnace in Mario Mart in the stage Grocery Villa.

Mario uses Yahoo! Mail