I read in a few magazines that the Beijing Olympics fireworks were faked on television using CGI. In fact the animators had been working on the 55 second video for a while, adding smog and even making the camera shake to make it realistic. Apparently they really did let off the fireworks afterwards. They only showed the fake one on TV, because the fireworks may have been too large and posed a danger for camera crews filming above.
Anyone else know this? I only found out the other day...