I still dont see why people are baffled by Boq's transformation in wicked is done. Its just a double that comes out painted silver and lipsynchs the "oh no" part.
not so much "how did they do that" but more "that is totally cool and beautiful" is the scene in Aida when the river turns into a canopy then just falls and takes on the shape of a tent, totally theatrical.
as for the car in Chitty, maybe it was because i had 'Chitty' seats (lol) but i london i could clearly see the arm that supports the car, if just comes up out of the stage with the car attached, the same principal of those electric company trucks that have the bucket thing that raises the technician up to the telephone pole.
what was also totally a treat to watch was the recent revival of Little Shop at the end when the plant came out over the audience, i was totally tickled by that.
http://www.flickr.com/photos/27199361@N08/ Phantom at the Royal Empire Theatre