Very cool! I won't be first to compare your game to cuphead, right? :)
Random thoughts: presentation was very cool- not only the fights, but even the moving around between cabinets between them.
Bosses were really well designed- both art and gameplay wise. Loved, that every one of them had three distinct phases, with different player mechanics!
Beating the guy with Debug.Log() was great. If this is not "makeshift", I don't know what is!
I couldn't aim up with my controller. Since this is a second game that gets this comment it may be my controller is busted :)
Controls could be a bit better. Sometimes it wasn't clear to me if I'm gonna clear the jump above the shockwave in first fight, or hit the fish in second.
The second fight was a bit buggy. There was no visible feedback when hitting the big fish in second phase, other than health bar getting smaller. Also- the big fish kept attacking after being defeated in phase 3 (I had the same problem with the duck in my game!).
Also- the level clear times at the end were a nice touch!
Those problems, however, did not mess up the enjoyment I got from your game!
Great work!