In Super Mario Maker for the Wii U, Mystery Mushrooms serve as a unique power-up that transforms Mario into various characters and objects, creating a delightful twist on classic gameplay. When Mario collects a Mystery Mushroom, he transitions into a form known as “Costume Mario,” which visually reimagines him as a range of characters from the Nintendo universe and third-party games, such as Luigi, Princess Peach, Goomba, Mega Man, and Link. Players can even turn Mario into items like a question mark block or a trampoline, all while retaining his standard size and gameplay abilities.

These transformations primarily affect visual elements and audio cues—changing how Mario looks and sounds when he jumps, taunts, or takes damage—but do not alter his core gameplay mechanics. For instance, while in a costume, Mario maintains the same hit points and does not gain or lose special abilities based on the character he resembles. Instead, the costumes function akin to power-ups; if Mario gets hit while wearing a costume, he loses the costume but continues on his journey without suffering a loss of life.

Players can unlock these costumes through two main methods:

1. Amiibo Scanning: By scanning specific amiibo figures, players can unlock pixel art versions of those characters to use with Mystery Mushrooms.
2. Completing the 100 Mario Challenge: Players can also earn additional costumes by successfully completing this challenge mode across varying difficulty levels. This method includes the possibility of unlocking costumes that are not tied to any amiibo.

After unlocking costumes, players have the option to select a specific costume for their character or let the Mystery Mushroom randomly generate a costume during gameplay. This feature adds a layer of unpredictability and fun, encouraging players to experiment with different character designs and sound effects as they navigate through user-created levels.

In summary, Mystery Mushrooms are an inventive gameplay element in Super Mario Maker, allowing for a whimsical visual transformation of Mario into a myriad of beloved characters and objects while preserving his essential gameplay mechanics and character size.