Cats have many folkloric associations with ghosts. In the UK, white cats were linked with ghosts, and black cats linked to death. While cats in Japan can be linked to good luck, the bakeneko were cats thought to be possessed by ghosts or demons, who could walk like humans, talk, and shapeshift.
While dogs seem like the better choice to train to follow commands, cats can also be trained. The important thing to know is that they have different motivation levels to dogs and will often consider the cost/benefit trade-off in learning to be much lower. Dr Mad needs to get himself a clicker and some treats!
SFX: Rub Rub
Prof Panda: Why are we at a cat cemetery? I'm tired.
Dr Mad: I have created a way to bring the dead back to life!
Prof Panda: That doesn't sound like a great idea.
Dr Mad: Once risen, my legion of the doomy will answer only to me and will take over the world!
Prof Panda: Legion of "doomy"?
Dr Mad: BEHOLD!
SFX: Click Click Click
Dr Mad: Who DARES to leave ectoplasm in my litterbox??!!