A Ghost on Film
This is incredible. Apparently this German commercial never aired because it caught footage of a real ghost. This could just be a very clever use of digital graphics, but if so, it's no amateur job.
About two seconds into the commercial look closely and you'll see something moving along the side of the car, a human-like ghostly white mist. Turn your volume up, and you'll be able to hear the very faint sound of a voice muttering.
The producers swore it was authentic. In any event, it is really eerie. Give it a minute to load, it should play on your browser:
(Forgive me. But go pull this gag on someone who trusts you, and you'll feel better.)