Many of the unlockable pictures in the galleries, as well as a couple of the dioramas, show scenes and enemies not actually included in the game. Of particular note is a piece of Concept Art showing King K. Rool in a new tribal outfit, implying that he was going to appear in the game at one point, as seen here◊.
There were going to be dinosaurs in the game. Live ones, not walking fossils like in the cliffs. Some unused concept art from Danny Richardson shows an enormous brachiosaur character, and art of the temple stage shows pterosaurs soaring in the background. A second jungle setting, named "Jungle 2", was also planned but ultimately dropped.