The bomb maniac should replace Mouser as it fits best. You can use any npcs for the other characters but not the koopatroopa's as it would be a bit akward when you jump on them and they turn into sheels or so. And also not the piranha plants.
The one npc after the cat is supposed to be a bee. The bee can replace any of the paragoombas but in a way after you hit it that it dissapears. The one after the bee is supposed to be a barrel which rolls on the way.
The last four npcs aren't needed.
Here's a video showing them off in case you need to know how they act.
