TV fans are used to having special effects in TV shows, but the scenes where special effects or a green screen/Chromakey are used are usually easy to spot, or at least we look at them and say "I bet that was camera trickery or green screen." This video shows that Chromakey is used in almost all TV shows, even ones you wouldn't expect.

This is rather eye-opening. The next time I see the camera go from David Letterman to Paul Shaffer on 'The Late Show' I'm going to yell at my TV, "green screen!"

[via Boing Boing]