Years ago I saw this series. I recall seeing three ghosts...one was female and looked kind of like a harpy, the others were male, one looked like a caveman, and the other looked somewhat like a cockroach. What were their names and what episodes were they in?
I don't think so. The female ghost had wings, a spiky hairdo, and was chubby. the cockroach wasn't a skeleton, the caveman wasn't a werewolf...he had longish hair, and wore a skin. I think they were in the episode that was set in China.
The female "ghost" sounds like Prime Evil's sister, but she had a more robotic look to her. The cockroach thing sounds like one of her robotic servants.
As for the caveman, I have no clue. The only episode I have on tape is when his sister visits, and she is chubby with spikey hair, and I believe she had wings sorta like a fly if I remember (in shape, not detail).