Super Mario 3D World
Super Mario 3D World
Almost every object in the game freezes in place when you die. Plessie is the only exception to this rule.
Contributed by MeleeWaluigi
An unused song, listed as "Mario3House02.sg.32.dspadpcm.bfstm" can be found in the game's data. It is unknown what or where the song could have been used.
Contributed by G-Haven
The level Mount Must Dash is a reference to Super Mario Kart, with the music being a remix of the Mario Circuits' music.
Contributed by Stryker94
According to the game's Producer, Koichi Hayashida, Peach was not originally intended to be playable at the start of development, and was intended to be the damsel in distress character as she is in other Mario titles. The idea of her being playable was brought up by the game's producer, Yoshiaki Koizumi, who told the team that Peach should be playable, stating "I think she adds a lot to the sense of competition when you get in multiplayer. You can have different people choosing different characters based on their personality or whoever they like. And Princess Peach is just really a lot of fun to play!"
Contributed by CuriousUserX90
The theme for the Captain Toad levels is the Toad Brigade theme from Super Mario Galaxy.
Contributed by Boyobmas
The end of the E3 2013 reveal trailer shows Mario making it to the top of a flagpole and being rewarded with 10,000 point as well as an extra life. In the final game, reaching the top of a flagpole only rewards the player with 10,000 points.

This was most likely changed because the player could use the Cat Suit to climb to the top of the flagpole, making it incredibly easy to get a 1-up every time they reach a flagpole.
Contributed by Boyobmas
The game uses the same death jingle as in Super Mario Bros. 3.
Contributed by Boyobmas
If Toad is at his smallest state, his head's color scheme changes from white with blue dots to blue with white dots.
Contributed by ScienceTheRatx
The idea of the 'Clear Pipe' came from the game's producer, Koichi Hayashida, wondering "What's Mario up to while he's in there?" while travelling through the iconic green warp pipes of the series.
Contributed by CuriousUserX90
8-bit Luigi spites can be found in various places throughout the game.
Contributed by Kodyurem
After beating the game, a Luigi-themed Mario Bros. game called Luigi Bros. can be played by tapping a Luigi button in the bottom left corner of the title screen. This can also be played right away if save data for New Super Luigi U is detected.
Contributed by Kodyurem
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Hidden halfway through stage 1 of Rainbow World is a cloud which will launch the player to a secret bonus stage consisting of tiles floating in space. Lighting up the tiles will reveal Link as he appears in The Legend of Zelda, accompanied with a disco rendition of the series theme.
Contributed by KnowledgeBase
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Director Kenta Motokura has said that the "Double Cherry" power-up was made after somebody on the development team made a mistake, accidentally placing two playable Mario characters into the same level.
Contributed by Dazz