Super Mario Maker

Costume Mario
Mario can take on unique forms upon touching a Mystery Mushroom, causing him to transform into Costume Mario. These costumes reference Nintendo and third-party characters, and most of them are easily unlockable by using the amiibo scanning function. There are 153 available costumes in total, 5 of which are from Splatoon.

Using a costume replaces the default sound effects and jingles with Splatoon-themed ones:
 * Course Clear: completing a level with an Inkling costume plays Hero Mode - Onward! from Octo Valley, while completing a level with one of the Squid Sisters costumes plays the City of Color jingle.
 * Lose a Life: falling into pit with any of the costumes plays Hero Mode - SPLAT! from Octo Valley. It is interesting to note that the Inkling Squid, Inkling Boy and Inkling Girl's fail jingles make use of the "splatted" voice clips, while Callie and Marie don't.
 * Appeal: posing with the costumes triggers relevant sound effects. The Inkling Squid, Inkling Boy and Inkling Girl use "This Way!" voice clips, while the Squid Sisters use their respective "Stay fresh!" voice clips.
 * Mystery Mushrooms: turning into a Splatoon costume adds the spawning sound effects at the end of the regular powerup jingle.

Inkling Squid
The Inkling Squid is the 62nd costume. He is unlocked by clearing a 100 Mario Challenge on Normal or harder, or by scanning the Inkling Squid amiibo. Pressing makes him pose, revealing his humanoid appearance. The Inkling Squid appears to be dark-skinned with green eyes, and he is wielding a Splat Roller and wearing the Studio Headphones, White Layered LS and Hunter Hi-Tops.

Inkling Boy
The Inkling Boy is the 63rd costume. He is unlocked by clearing a 100 Mario Challenge on Expert or Super Expert, or by scanning the Inkling Boy amiibo. Pressing makes him pose with a Splattershot. His appearance is identical to the Inkling Boy amiibo.

Inkling Girl
The Inkling Girl is the 64th costume. She is unlocked by clearing a 100 Mario Challenge on Expert or Super Expert, or by scanning the Inkling Girl amiibo. Pressing makes her pose with a Splat Charger. Her appearance is identical to the Inkling Girl amiibo, spare the charger in place of the usual Splattershot.

Callie
Callie is the 152nd costume. She is unlocked by clearing the Squid Sisters vs. Bloopers Event Course as Callie, or by scanning her amiibo. Pressing makes her strike her signature pose seen at the end of the Inkopolis News, as well as in various promotional artwork. Her unique squid form is also visible when crouching or swimming by pressing.

Marie
Marie is the 153rd costume and therefore the last one. She is unlocked by clearing the Squid Sisters vs. Bloopers Event Course, this time as Marie, or by scanning her amiibo. Pressing makes her strike her matching signature pose. Just like Callie, crouching and swimming reveal her unique squid form.

Unused gear icons
Gear icons from an unknown prerelease version of Splatoon were present in the game's files. 23 pieces of headgear, 19 pieces of clothing and 12 pairs of shoes were found in total. A majority of the items are recognizable, but a couple of the sprites use sample textures. Others seem to have been either scrapped early on, or possibly repurposed. The Warrior Headdress, the Varsity Hoodie and the Shirtstravaganza are notable scrapped elements.