What Could Have Been: The game includes a rather fascinating library of concept materials unlocked by obtaining the hidden Platinum medal on each of the bonus challenges, including more than a few scrapped enemies (most of which are variations upon the classic "Dracula" vampire design) and even a few unused levels. Among the unused levels are some incredible-looking environments:
The Bakery looks a lot like a cross between the Kitchen and the Workshop, with kitchen implements on numerous tables and a large oven in one corner.
The Gallery was a wide-open space with paintings and easels strewn about.
The Museum may very well have been the largest room in the game, featuring innumerable displays ranging from a pirate ship to several Venus Fly Traps (which are pictured in other concept art as rejected enemies).
The Observatory was more like a planetarium from the artwork, with a complete model solar system and several other celestial dioramas.