Frankly Speaking

I'm not an American Idol fan anymore but I did see this - and I agree, very cool. How did they do it exactly?

I was debating this issue with someone last night, and it turns out I was right.

The answer is here

"Finally, all three elements — Dion by herself, Dion with the body double and the original Presley performance — were combined through editing and a technique called rotoscoping, which traced Presley from the original footage by cutting him out.

"Rotoscoping allows you to take one image from a pre-existing piece of video and puts him a whole new environment — completely new use of that same piece of video," Disney digital media designer Joe Husung said.