Though the game doesn't arrive in North America and Europe until September 11th (Japan on the 10th, Australia on the 12th), it seems some members of the media already have Super Mario Maker in their hands and on their Wii U. As such, one such person has shared an image to Miiverse of a Mario who has been Megafied (thanks to amiibo) reaching the goal of a level:
For those who haven't heard, amiibo can be used to give Mario a sort of power-up which transforms him into a regular Mario-sized version of the character in the style of the original 8-bit Super Mario Bros. No fancy abilities or anything (so no pew-pew for you-you), just a skin that gives Mario an extra hit.
Also, you needn't worry about actually owning the amiibo in order to access this or other such skins. Word has it that there's a way to unlock them just by playing the game.