The instruction manual for Kirby's Block Ball shows artwork for Propeller, Chuckie, Coner, Waddle Doo, Pengi, and Sir Slippy. However, Pengi and Waddle Doo are not seen in the game. They were planned to be included, but we're removed for unknown reasons.
The game has some grammatical differences between regions. One example of this is that the Japanese language doesn't use an 'S' to signify a plural.
The game intro and title screen were completely redone. In the Japanese version, Kirby comes from the background and bounces onto the game title and then starts spinning around. In the international version, Kirby floats on a cloud and then jumps down to the title screen.
There are two unused, but fully coded enemies present in the game data. The first one is Pengi, whose graphics are loaded on Stage 7-2 but never used. The other is Waddle Doo, who is not loaded on any of the stages and has a death animation in which his eye pops out, which might be why he was never used.