Mind of His Own

Let's say you want to be a ventriloquist, like Ralph did.

Would you go to a toy store to buy a dummy, like Ralph did? Only one -- a used dummy that looked like a professor -- was available. Ralph bought it immediately.

Ralph brought the dummy home, put a show together, and started appearing. But something very strange happened at one performance. That professor dummy started talking and answering questions...but it was not Ralph's voice.

Why?