Mymy64
Monty Mole
I feel like this would add some much needed variety to the enemies as they help spice things up. For example, B1-5 could just be the regular ghosts, but after that you start fighting ghosts such as Diffuse Goobs that spawn Mini versions of its self, Bomb Oozer that throw Bombs at you, Regen Hammers that can rejuvenate themselves, and Lethal Slinker that can kill you in one hit if you aren't careful(I choose the lethal one since the Slinker doesn't attack very often). All of these could make the combat more interesting and not as repetitive.
