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: In the alley, Bruce places two roses on a sidewalk and then walks away. But when Vicki gets to the roses, they have changed positions. (00:46:50)
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.
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 Batman is gliding down to get Napier, there appears to be nothing attached to his belt, but when he is about to land, his rope gun has magically appeared on his belt. (00:26:40)
Continuity mistake: When Batman initially fires the rope around Joker's ankle at the end, the rope only goes around the statue's legs. The next time we see it, it's somehow re-tied itself, and is now looped around the statue's backside. (01:52:55)
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.
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)
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.
Continuity mistake: In Joker's hideout, Bob gives Joker the pictures he took and throws the folder that the pictures were in on the floor. But later in the shot above the room, the folder is no where to be found. (00:53:05 - 00:54:00)
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.
Continuity mistake: At the cathedral scene, when Batman & Vicky are hanging at the ridge, and the Joker is about to be picked up by the helicopter, the color of Joker's jacket changes from purple (front shot) to red/orange (shot from above) and back again. The orange one may be his blouse, as it has the same colour visible under his jacket in the front shot. Then, the same jacket and hat are seen hung over the gargoyle just a few seconds later.
Continuity mistake: In the scene where the Batmobile automatically drives to Batman's and Vicky's location, a couple of patrol cars start following the Batmobile. When the Batmobile reaches Batman, they have mysteriously disappeared. (01:12:16)
Revealing mistake: When Batman drives the Batmobile into the Axis Chemicals factory, watch closely when he slams through the first gate - you can see the gate is swaying and starting to open before the batmobile hits it, indicating it wasn't really closed and was left unlocked and partially open to make it easier for the stunt-driver to drive the Batmobile through it.
Audio problem: Unlike the second movie, the jet engine sound was not dubbed over the piston engine sound. The fact is, the jet engine in the Batmobile is a fake.
Revealing mistake: When the Batjet crashes, if you pay close attention to the scale of the jet, cars and buildings in relation to the scale of the fire and explosions, it is very clear that this scene was created with models.
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.