Continuity mistake: When Curly Bill is shooting up the town while drunk, he fires about 10 more rounds than his six shooter can hold without reloading (so too many shots even if he had a second gun), and still has a round remaining when he shoots Marshal Fred White. In the 1880 court hearing held after Marshal White's death, Curly Bill still had 5 rounds remaining in his pistol.
Continuity mistake: When the bobsled team is getting their act together in Calgary, there's a scene of them pushing off with an unpainted bobsled. In the shots of the feet of the guys pushing at the back of the sled, you can see that the lower back of the sled is painted black with green stripes, the colours that they paint the sled in a scene a few minutes later.
Continuity mistake: At the beginning, when the president lands in the helicopter, the shots go back and forth between the rotors spinning, and the rotors stopped. (00:02:10)
Continuity mistake: When the two Ninja robots fight, the robot on the left loses his head before the blade strikes.
Continuity mistake: When the jet crashes, we see a shot from below showing a large portion of it poking out over the cliff. We then cut to the parachutists, and when we cut back to the jet, we see that very nearly all of it is safely on rock.
Continuity mistake: When Wednesday and Pugsley are playing with the guillotine, Wednesday has a scroll in her hands, which she then rolls up. The shot changes and you can still see the rolled up scroll in her hands. However, the shot then changes again and you can now see Wednesday rolling up the already rolled up scroll.
Continuity mistake: When Dennis is in Mr. WIlson's bathroom after his bath, pouring mouthwash in his nose spray, Dennis has toothpaste all over his chin and mouth. When they show Dennis from the side, it is gone. From the front it is there again. This happens several times in the shot.
Continuity mistake: Kimble dyes his hair very dark to escape detection and dyed hair fades over time. For the rest of the movie his hair noticeably goes from darker shades to lighter shades and back again showing that the scenes were shot non-sequentially on different days with a fair amount of time in between.