Mary O. is the manual guide from Super Mario Maker, and she sadly does not have enough fan art of her. to the left is a picture I found off of Tumblr.
Mary O. is known as Mashiko in Japan, and she is not alone in her work of helping the player make levels in Super Mario Maker.
Mary O., Yamamura, and Undo Dog
You were the right choice for this Waifu Wednesday!