Here on a xbox forum they talk about 23 pets (black cat including)
1 - Slime - Petri Dish from Chests or Gold Chests
2 - Guinea Pig - Cabbage from Dragon Snatcher, Chests, Gold Chests
3 - Zombie - Brain from The Groom, Gold Chests, Shadow Chests
4 - Bat - Vial of Blood from Vampire Miner, Gold...