Unused music found in the data for the June 2004 Japanese demo of Paper Mario: The Thousand-Year Door (then known as Paper Mario 2). The track’s internal filename is BGM_EVT_NOK1, which can be deciphered as “background music for an event in Petalburg”, since the Petalburg area has an internal code of “NOK”. The music is not found in the game’s finished version.
_{Main Blog | Twitter | Patreon | Store | Small Findings | Source}

The music track playing during the intro to Super Mario Odyssey, extracted from the game’s files so it can be heard without the sound effects that are usually present. Note that at 59 seconds, an orchestrated version of the Super Mario Bros. Airship theme from Super Mario Maker plays; this is to date the only time when Super Mario Maker music was used in the main Mario series.
_{Main Blog | Twitter | Patreon | Store | Small Findings | Source}

The music for the Galaxy Colosseum from Mario Kart Wii. The Galaxy Colosseum is a battle stage that, while present in the game’s files, was only available to be played during three online tournaments in June 2008, June 2009, and March 2010 respectively. After the final tournament, there is now no longer any means to access this stage in-game and hear the music without modifying the code.
_{Main Blog | Twitter | Patreon | Store | Small Findings | Source}

Unused 8-bit version of “Boss Bossanova” found in the data of Donkey Kong Land 2. Boss Bossanova is the regular boss battle music from Donkey Kong Country 2; it plays in all boss levels except against the final boss, which uses Crocodile Cacophony instead. In Donkey Kong Land 2, however, every boss fight uses Crocodile Cacophony, leaving the regular boss music unused.
_{Main Blog | Twitter | Patreon | Store | Small Findings | Source}

In Paper Mario: The Thousand-Year Door, Princess Peach can enter the room to the left of her starting point in all her gameplay segments, where she is able to take a shower. While showering, she will randomly hum one of three short tunes, which are extracted here from the game’s data. The first one is the Super Mario Bros. main theme, the second one is the Super Mario Bros. water theme, and the last one is the Super Mario 64 Peach’s Castle theme.
_{Main Blog | Twitter | Source: files extracted by me using a GC emulator, game: PM: TTYD (NA, GC)}

The “Mario Special Disc July 2002″ was a Japanese Super Mario Sunshine demo disc produced for E3 2002, containing a demo with six playable missions and three video commercials for the game. This track plays in the disc’s main menu, and due to being unique to a piece of official Super Mario Sunshine media, is technically a Super Mario Sunshine song.
_{Main Blog | Twitter | Patreon | Store | Small Findings | Source}

The European release of the NES version of Wario’s Woods has unique music added that is not present in the other releases of the game. Here is a comparison between the boss themes used in the Round Game mode. From 0 to 38 seconds in this track, one loop of the US/Japanese boss theme plays. From 38 seconds onward, the European boss theme plays.

The main mansion theme of Luigi’s Mansion has several different forms: an instrumental one, three different variations of Luigi humming the song (high, medium and low health), a version with ghost sounds, and finally Luigi whistling the song. In-game, these are separate tracks of the same song; they are played simultaneously while all of them are muted except the active one, in order to be able to switch between the forms without having to load music into memory.

Here is how the song sounds with all its tracks active at the same time. Three Luigis are humming the melody while another is whistling.
_{Main Blog | Twitter | Patreon | Store | Small Findings | Source}

In 2008, a campaign was featured on Nintendo of America’s website where the visitor could construct a wishlist of select Nintendo games for the holiday season. Then, upon entering a phone number, an automated message of Charles Martinet speaking as Mario would be sent to that number where Mario would deliver the wishlist to the recipient. Here is a recording of a sample message that could be constructed.
_{Main Blog | Twitter | Patreon | Store | Small Findings | Source: twitter.com user “robotortoise”}

The ending theme to Paper Mario Sticker Star has two phases: saxophone-only and saxophone with orchestra. In-game, this is achieved by separating the music into two track: saxophone and orchestra. It is impossible to hear the second track in-game by itself. Here it is isolated.
_{Main Blog | Twitter | Patreon | Store | Small Findings | Source}