Unfortunately this glitch doesn't have any uses speed-wise but I thought that someone reading this might be interested in this anyway. Basically, if you shoot backwards while collecting the gem, you get put in a weird state where you seem to control the projectile but the game also makes you take control of a random enemy. Funnily enough, in the chest room, you take control of the chest rather than the mini boss (though this isn't showcased in the video).

Controlling it and which room you want to enter is pretty finnicky and I haven't quite worked it out. Anyway, here's a demo

What a find. Haha. Nice work.

Oh man, that's awesome.. hahahah