Today I discovered that the original trailer for Tron is actually pretty interesting for several reasons. It contains footage that isn’t actually seen in the final film (the animation of the MCP being most notable), many colors and some background images that were changed in the film, very different sound effects and music, and it even begins with a view of the computer that supposedly hosts the MCP, called the “Encom 511”. Definitely worth a watch:
Ooh, I just saw this one! I’ve been going through the supplemental stuff on the LaserDisc set, and they have a whole series of (I think) eight alternate trailers! Most of them are in this segment although the video quality is awful, lol)