Costume Mario

Costume Mario is the form Mario takes after touching a Mystery Mushroom in Super Mario Maker, allowing him to transform into numerous Nintendo and third-party characters, objects and groups or combinations thereof. Upon scanning certain amiibo onto the Wii U GamePad's, an 8-bit version of the amiibo character (16-bit if a Sonic the Hedgehog amiibo is used) will be unlocked in the course maker, allowing the player to use it any time from then on without having to scan the amiibo again. In addition to amiibo characters, Mario can also transform into certain objects, such as a ? Block. Costumes can also be unlocked through the 100 Mario Challenge mode, including the characters which have amiibo unlock conditions, or by completing certain Event Courses.

According to Nintendo's website, nearly every Super Smash Bros., Animal Crossing, Splatoon, and Mario-related amiibo are compatible, as well as the Chibi-Robo and Wolf Link amiibos for their respective costumes. There are a total of 153 costumes in the game so far, consisting of 100 base costumes (95 of which can be unlocked by completing the 100 Mario Challenge), and 51 additional ones that are gained either from Event Courses, free updates, or as of update version 1.40, playing 100 Mario Challenge on the Normal, Expert, and Super Expert difficulty levels. It is currently unknown how many total additional costumes will be present, though there's a chance that 99 additional costumes will be added to the game. Each costume that can be unlocked via the 100 Mario challenge can be unlocked randomly at a fixed difficulty tier. Completing the 100 Mario challenge in a given difficulty gives a chance to unlock a costume from that difficulty or lower.

This power-up was conceived after the development team was struggling to find an interesting and effective use of amiibo for the game. According to Takashi Tezuka, the art designers pitched the idea of changing Mario's sprites after drawing some of the amiibo characters in a pixel art style.

Costume Mario functions the same as Super Mario, but with Small Mario's physical stature; although some of the costumes are slightly larger. While Mario wears a costume, he cannot wear any Shell Helmets or collect a Fire Flower. In addition to appearance, various sound effects may also be changed to reflect the character, such as the jumping sound effects and "Course Clear" fanfare. The power-up sound effect may also be replaced by a different sound effect from the character's home series. The non-DLC Pokémon series costumes are notable for lacking special sound effects, instead using the standard Super Mario Bros. sounds. Each character has a unique pose if the player presses and holds. The messages seen after finishing the 10 Mario Challenge and the 100 Mario Challenge also varies depending on the appearance of the player.

Mario can only transform into Costume Mario in the Super Mario Bros. style of the game. If the player changes game styles while Mario is in his Costume Mario form, he'll either change into Raccoon Mario (Super Mario Bros. 3), Cape Mario (Super Mario World), or Propeller Mario (New Super Mario Bros. U).

The costumes do not follow the graphical limitations of the NES. Most of them are designed to follow the characters' official designs, usually using more than 3 colors.

As Mystery Mushrooms won't be included in Super Mario Maker for Nintendo 3DS, the Costume Mario form will not appear in the game as well.

Originally, the costumes were known as Mystery Suits.

Trivia

 * On several occasions, costumes have been released out of order. Despite being costume number 112, the Sky Pop costume and the sponsored Event Course in which it was introduced were released after costumes 113 to 118. Similarly, the Event Course costumes 129 to 131 were released after Wolf Link (unlocked by amiibo) and the 100 Mario Challenge costumes 133 to 144, which were released with the 1.40 game update. Finally, costumes 152 and 153 (Callie and Marie) were released before 150 and 151 were announced.
 * Before the version 1.41 patch was released on March 17, 2016, in the English versions of Super Mario Maker, the Wolf Link costume text was in Japanese.
 * Along with the Wolf Link event course, an event course for a Mary O. costume was released, with "test" as its title and description, implying an error concerning a premature release of the course. It was soon removed from the server, but was still playable in the time it was up, granting the players the costume early.