There are multiple instances of leftover data from the original Demo for the game that were accidentally kept in for the final release. For example, Mario's sprites for when he's speaking rarely switch into his original face set (and also having no recorded dialog).
Mario and Luigi have unused facesets of them being covered in blood/hurt. These were never used, and Luigi's hurt faceset was also left in the files for The Nightmare Begins Demo.
When Mario first meets Foxy, there was originally going to be an option where Mario could use a sword prop on Foxy, however this was scrapped.
The Cupcake makes no appearance in the game, though the recycled dialog from EthGoesBoom is credited to play the Cupcake itself in the credits. According to the developers, the Cupcake was removed due to coding difficulties. In the files, there are sprites for the Cupcake, Mario also has dialog for interacting with the Cupcake, and there are two audio files for the Cupcake left in for the scrapped plan.
Mario has alternate dialog for interacting with the Janitor's Closet before being unlocked, which was a complete different recording of his voice-line, though it was left unused for unknown reasons.
