Revealing mistake: Right after Joker falls off the top of the cathedral, Batman and Vicky fall too and we catch them three times before Batman's grapple digs into the stone. On the second and third time you can actually notice Vicky's face expression doesn't look one bit scared, so you know they're not falling. You can also see there's a screen in the background. (01:58:40)
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: 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 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.
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: 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.
Revealing mistake: When the Joker is in the basement getting surgery, he walks up the stairs laughing and when you see the side of his body before the end of the scene, if you look closely, you can see that his face is still normal Caucasian tone.
Continuity mistake: When Batman jumps off of the remaining bell at the top of the cathedral, the goon uses Batman's momentum to throw him into a set of stairs, his trajectory parallel with the near wall. Since the goon wasn't standing near the wall when he threw Batman, this angle would not be possible to achieve.
Continuity mistake: When Joker and his goons are trashing the paintings, Joker writes "Joker Was Here" on the painting by the statue. In the next shot the painting disappears.
Continuity mistake: In the scene where Joker has broken in on the mayor's televised speech to the citizens of Gotham to challenge Batman to a "big duke-a-roo", Bruce freezes the live broadcast on a close-up of the Joker. He then flashes back to his parents murder. After the flashback, he looks again at the freeze frame picture of the Joker, but it is a different picture. When he freezes it, Joker's eyes are closed. When he comes back to the picture, his eyes are open.
Visible crew/equipment: When Batman comes through the skylights in the museum just after Vicki throws water on Joker's face, you can see the stunt cable that lowers Batman down. Batman does use a system of cables and grappling hooks because he has no superpowers, but the cable lowering him down disappears as soon as he hits the ground. It was used to lower the actor down safely, not the character.
Revealing mistake: When the Joker first appears, you can see a purple splodge on the left side of his neck.
Revealing mistake: When Vicki is driving the car Knox jumps on, you can see it's a stunt driver in the wide shots.
Continuity mistake: When Bruce smashes the vase in Vicki's apartment, it's further from the wall in the initial shot than when we see it actually smash in the close up.
Continuity mistake: When Joker sees himself for the first time he hits the light and the bulb smashes against the wall. In the wide shot the light is still swinging and you can see that the bulb is intact.
Revealing mistake: In the beginning, the first shot we see of Batman (a shot from above where he turns and walks into a doorway, casting a shadow behind him) is quite obviously animated. He literally looks like a cartoon... because he is one in this shot for some reason.
Answer: Most likely, in real life, this would be impossible. Movies take liberties with facts and realities in order to tell the story.
raywest ★