Continuity mistake: When the Joker's henchmen are trashing the museum, one guy puts red handprints all over a portrait, later the Joker walks by the same portrait and the handprints are gone. (00:59:55)
Continuity mistake: After Batman rescues Vicky he has a voice remote for the Batmobile. As the car approaches he orders the car to stop by speaking into the remote and then lowers it to his side. When the camera shot changes showing the car stopping right in front of him, he is still holding the remote to his mouth. (01:09:20)
Visible crew/equipment: When the Batmobile is driving itself to Batman and Vicky Vale, you can clearly see a hand turning the steering wheel. (01:12:00)
Continuity mistake: During the beginning of the parade sequence, the green-haired, big-nosed balloon is shown being decently high with the Joker's float underneath it. Yet when the Joker is shown dancing in a few close up shots, the face of the balloon is directly behind him.
Continuity mistake: When Joker is at the top of the building and taunting them, his chin is red (presumably from his blood when Batman socked him in the jaw.) After he falls off the building, and we see him lying on the ground, his chin is not covered in blood like it was before. (01:50:45 - 01:54:35)
Continuity mistake: When the "automated" Batmobile is sent into Axis Chemicals to blow it up, six of the Joker's men are shooting at it before it explodes, killing or seriously injuring everyone. Three of these same henchmen are also on the Joker's parade float at the very same time or very shortly afterwards in Gotham Plaza and one of them flies the Joker's escape copter at the end of the movie.
Revealing mistake: When the Joker is having the party with all the balloons, Vicky Vale tries to escape from the gas by getting into a car. If you look at the back window while she is driving off, the window is rolled down, which would have led to her death, not to mention motor vehicles are not air tight to begin with.
Revealing mistake: At the end when they show the Joker dead on the pavement after he fell, look closely during the first few seconds of the shot and you'll see him blink twice. (01:59:05)
Continuity mistake: When the Joker is shooting Carl Grissom wildly, you can hear the sound of the glass behind him being hit only once. Later when the Joker is sitting at his desk, you can see two bullet holes to the left in the glass.
Continuity mistake: During the Joker's parade, shots looking at the Joker from the side show that his float passes the same shop twice.
Continuity mistake: Harvey Dent is on the telephone while smoking a cigar that is partly ash. Two camera angles later he is smoking a brand new cigar with no visible ash. (00:58:25)
Revealing mistake: Harvey Dent and the mayor argue in Dent's office which has an unusual semicircular shape. In the next scene, Alfred uses the telephone in Wayne Manor, and you can see that it's the same room, just with different furniture and dressings. (00:56:10)
Continuity mistake: When the mimes open fire on the gangsters, watch the police officers to the left and right above them on the top of the steps. In the overhead shot, right after they open fire, they disappear. (00:49:30)
Continuity mistake: Vicki has five photos of Bruce Wayne on a table. She picks one up, but when she is looking at it, through the back of the photo paper the snapshot looks different from the one she picked up. (00:52:30)
Continuity mistake: At the beginning of the movie when the police are standing outside of Axis Chemicals, Eckhardt has very distinct facial hair. In the next shot when they are inside the plant he is clean shaven. (00:23:05 - 00:24:10)
Continuity mistake: At Axis Chemicals, Jack's face is cut by broken glass and has blood gushing out of it. But in the next shot, Jack (probably the stunt double) does not have any blood on him as he goes over the edge of the rail. (00:29:00)
Revealing mistake: When the shields of the Batmobile are engaged, the metal plates come from nowhere. There isn't a place for them to come from or go to when taken off. And if you watch carefully, the shields coming from the sides of the Batmobile come out of thin air. (01:09:10)
Continuity mistake: When Joker's dead body is shown, the rope around his leg that was tied to the gargoyle is gone.
Revealing mistake: When Jack and his goons are breaking into Axis Chemicals, there's a scene where they're cutting the lock off of a safe. When the safe door is opened, you can clearly see that there is no locking mechanism in the side of the door.
Plot hole: Right after the Joker goes into the cathedral with Vicky, Batman follows him with no one else entering in between the two parties. How then did Joker's goons get to the top of the cathedral before Batman or the chopper? They couldn't have planned it since Joker had to tell them where to pick him up, and they didn't know he would chase after Vicky to that particular location.
Answer: He was suspicious, but when she first entered the penthouse and Grissom said to leave their business meeting, he noticed the sexy facial exchange Alicia and Jack gave each other.