Epic had mentioned this scenario at least once in talking about plans unfinished I believe back at the Epic Megaboard Jazz forum.
Some or possibly all of these are still in the game. Using the sprite loop trick developed by Bluez, which is to construct a level with an end-level event that can be hit but the character will not be able to land on their feet (such as keeping them in a suction tube), some of these will show up along with normal sprites and other unused ones (edit: at the time when Jazz is supposed to run off the screen).
On that subject of unused sprites also mentioned here, using different methods of keeping Jazz/Spaz off their feet locks them into the different area in the sprite cycle which allows you to see different areas from the library.