This is the infamous "Ultimate Noob Boss" made by Iceguy. It is now back with a new name that implies it can be used for more than boss fights. It has quite a few attacks and is very customizable. Read the comments in the .asm file for details.
Idk if is just me, but this still hasn't fixed the sprite generating issue where as the first 2 enemies that are spawned on screen won't get hurt by Fire Mario's Fireball, without killing the first 2 sprites, the 3rd and higher sprite can die by the fire flower like normal. Hope that get's fixed someday.
Yeah, it was strange physics bug with how gravational acceleration and terminal velocity works, when the sprite jumps, it goes up as normal, but when it starts falling, it accumulates its downward speed quickly as if it was forced into the ground by telekinesis.