Revealing mistake: After Flynn, Tron and Ram take their drink, they resume their journey in their stolen Light Cycles. There is a shot of them coming around a corner and riding along a cliff side. If you look carefully (this is painfully obvious if you go frame by frame) they don't actually come around the corner. Their Light Cycles simply appear one by one and they make their turn. (00:50:40)
Revealing mistake: When the first of the blue bikes hits the wall and makes the hole, there is a rubber tyre bouncing away from the explosion. Any time that you see the back wheel of the cycles, there is no rubber tire. This is supposed to be the digital world. Even the tanks, with all the accompanying sounds does not have rubber on the tracks, as there are no tracks.
Revealing mistake: When Alan gets up to go to see Dillinger, look at the cubicles. The first row that Alan came out of is real. In the immediate next row, the cubicle that is adjacent to Alan's has no visible exit, and the two that would be heading toward the white wall seem to be only leading to each other. The rest of the cubicles in the area are all a matte painting used to extend the set.
Revealing mistake: With the exception of the set up and ending "real world" sequences, this is all in the digital world. There is no sun, yet when Tron, Flynn and RAM are drinking at the pool of energy, there is a reflection of what appears to be a plaza and a bright day outside the windows.