Continuity mistake: After rescuing Vicki from the museum, Batman leads Joker's henchmen on a downtown chase with the Batmobile. One car on his tail causes a major pileup at the intersection near Monarch Theatre. A short time later when the unmanned Batmobile is making its way down the street, it passes right through that very same intersection. This time, however, there are no indications that a pileup ever took place just moments before. All mangled vehicles and debris have disappeared. (01:08:20 - 01:12:00)
Factual error: The Bat signal at the end would not show up like it did in the film. In order to be as clear as it was, as well as visible, it would actually have to shine onto a surface, not just the clouds. They made this same mistake in Returns, but made it believable in the clouds (just not as sharp) in Forever.
Character mistake: The newspaper that reveals the combination of products that activates the Joker's poison has at least two grammar mistakes on the front page. The word "deodorant's" should not have had an apostrophe, and the word odoreaters was spelled "odoureaters," which has the British spelling of the word odor (Gotham City is obviously in the United States, not the UK). (01:17:10)
Continuity mistake: While Vicky is talking with Bruce at the Batcave she has some tears on her face which disappear between shots.
Revealing mistake: After the Batmobile's pair of machine guns riddles a straight line of bullet holes through a bay door of Axis Chemicals, it drives in and eventually goes on to blow up the plant. It might seem like the bullet holes themselves would weaken the bay door enough for the Batmobile to push through. But instead - as the bay door falls to the ground - notice how a ready-made seam splits apart directly above the line of bullet holes. (01:34:15)
Other mistake: In the scene at the beginning, when the robbers take Harold's wallet, the robber who had the gun says "American express card" but, when he says "don't leave home without it" the subtitles say the goon on the left says it, even though you can see the goon on the right move his mouth. (01:04:30)