Well... The most active and persistent members like Christian Game Maker and Antikore probably remember how the crushers looked when just a system and shape for those was created. Now you can see how crushers are looking now after redrawing sprites and adding decorations.
You can rewatch a video about the crushers
here.
One small crusher uses 4 extra sprites and huge one add 2 more extra sprites. In addition, let's say if you would like to make crusher that comes from below and that would hit the ceiling this would need more 2 or 3 extra sprites depending on how big those are. If you wouldn't know that additions are enemies then there wouldn't be even any new enemies at all. So this is why, I would like to suggest more extra sheets or... Why even not a sprite manager?