The file that contains the character scripts for Kertsi is named "Navi". Since Kertsi plays a similar role to that of Navi in The Legend of Zelda: Ocarina of Time, this is likely a reference to said game.
The game contains several unused stickers:
• A bigger version of the Leaf sticker.
• A Piranha Plant sticker.
• A Rock sticker.
• A Spiny Egg sticker.
• A Super Leaf sticker.
• A bigger version of the Leaf sticker.
• A Piranha Plant sticker.
• A Rock sticker.
• A Spiny Egg sticker.
• A Super Leaf sticker.
The game contains files for Super Mario Bros. 3's Ptooie enemies, suggesting that at one point they were planned to be included in the game.
While using the Boom Box Sticker in combat, a remixed version of the Space World theme from Super Mario Land 2: 6 Golden Coins will play
To date, this is the only Paper Mario title to not begin in Mario's house. Mario's house never appears in game.

Though he never appears in the plot, Luigi can be seen sitting in the backgrounds of 5 different stages. Using paperize, the player can even pull him off the page where he will run off screen. Every time the player does this, the left-most house in the Decalberg Suburbs will have a humorous newspaper article about Luigi being spotted in that location. If the player finds him all 5 times he will appear leading the parade during the credits.
If you tilt the 3DS at any time during gameplay, the shiny stickers on the touch screen will shimmer, like real stickers.
A segment of the Snifit or Whiffit minigame music uses the same tune as the Super Mario Bros. 3 Toad House Minigame.