List of Hotel Mario pre-release and unused content
From the Super Mario Wiki
This is a list of pre-release and unused content for the game Hotel Mario.
A "Cheese Hotel" was proposed during the concept phase and had concept artwork drawn for it, but the development team refused the idea and the artist responsible for it was replaced.
This is stored in the data for the final level, oddly enough. Also, the voices of Mario and Luigi are different, which are based on their respective voices in the DiC series. There is also an audio file of a placeholder voice actor explaining how to play the game, suggesting that the game would have contained a tutorial like the Zelda CD-i games. In the final game, Mario simply states during the intro to check the instruction booklet for help. In addition, each hotel was originally going to have individual level clear themes. Remnants of this can be found in the game's data.
Each hotel has an internal music, graphics and enemy data file, labeled from L1 to L8 (with L0 as two demo files). However, L6 is missing entirely from the list. The game's files show that a hotel would have appeared between Ludwig and Wendy's hotels, as the game skips from L5 to L7. There are no files associated with the hotel, skipping it entirely. This points toward Iggy being planned to have had a hotel of his own, as opposed to appearing in Bowser's.
An article announcing the game in the UK CD-i magazine implies that Yoshi was originally the character kidnapped by Bowser instead of Princess Peach and did not mention Luigi being present. However, this could be an error on the magazine's end. This was also the description provided with pre-release copies of the game, though they were largely identical to the final game.