The Ghost of Christmas Past
The Ghost of Christmas Past was one of the ghosts in The Real Ghostbusters in episode "Xmas Marks the Spot". While not much is known about her, she is well spoken when she speaks and is also away of events.
She spoke a little during the episode, and what is gathered is she is intelligent and aware of current events. When she was accidentally captured, Peter Venkman impersonated her until she and the other ghosts were released.