Ooooh I'm psyyyychic. ^^ I'm going to go read that now!

Also, yesss. Flies. Oh, and the vengeful undead kitty head item.

Nightmare pets in general are amazing! The thing that the wiki for Subeta does well is it not only describes pet species, but the pet colors too. So I can imagine what a nightmare sheeta looks like and that's a perfect pet species for a BOI pet. :D

Good luck on your item hunting. Also, undead animals of any kind. I know Isaac had a dead cat, and also a cricket at one point, or at least the head of a cricket. OH, and I think rubber cement might be an actual Subeta item, or at the very least craft glue is.

Actually, Cricket is another cat! Cricket, Guppy and Tammy are all actual cats belonging to the game creator. Guppy is one who was very special to him and his wife (the kitty sadly passed away a few years ago), so that's why he has so many items in the game, as well as a transformation if you collect enough of them. Guppy lives on!

You're very right, the vengeful cat head is one I thought of immediately. Probably some of the more demonic items as well? There's fetus-themed items on Subeta as well; another great place to start.

OH! I didn't realize Cricket was actually a cat! Ok. THAT makes the whole thing make more sense. I was like "HOW does he have a cricket head!"

The Guppy transformation is really awesome. My friend described it to me and it's adorable. Guppy should always live on.