Revealing mistake: When the reporter dies on air, her face is contorted into the Joker's face. When the camera is in closeup on her face, the "dead" woman's bottom lip moves.
Continuity mistake: At one point during the car chase through downtown Gotham City, the Batmobile maneuvers a sharp turn with the aid of a cable that launches from the driver's side and hooks onto a steel beam structure nearby. But as the Batmobile starts cornering, notice how the cable appears fastened in a different manner. Between shots, it has tied itself completely around the beam instead. (01:08:15)
Continuity mistake: Towards the end of the gunfire exchange scene at Axis Chemicals - from the point at which Joker was pondering an escape on the catwalk until Batman turns around to see the shadow of a police officer closing in on him - notice how the exit bears an altogether different appearance between views. (00:27:35 - 00:29:40)
Revealing mistake: When Jack falls into the chemical vat it's obvious the vat is quite shallow as he doesn't actually sink into the chemicals but instead just kind of lands and then sits there as liquid splashes out around him. To top it off, the subsequent shot of him disappearing into the chemicals is reversed as several bubbles can be seen 'unpopping' and growing smaller.
Continuity mistake: When Batman and Vicky are running from Joker's museum plot, and are running from Joker's henchmen, he shoots a cable up to a walkway. As the camera shows him firing, he fires the rope at a 45 degree angle, yet when he and Vicky are going up on the rope, the walkway is directly above them and the rope is perpendicular to the ground.
Revealing mistake: In the film's ending shot, the sky can be seen to flutter as the camera pans up, revealing a backdrop.
Revealing mistake: When Batman fires rockets at the Joker, none come out, instead a sound effect is used which cuts to explosions on the road where Joker stands.
Audio problem: Bruce watches Commissioner Gordon on tape at his party. In the first part, the audio is laid wrong and their mouths don't match.
Continuity mistake: When Joker comes to Vicki's apartment, Joker shoots Bruce and Bruce plays dead. As he plays dead, his right hand changes positions between camera angles.
Visible crew/equipment: In the museum rescue scene, as Batman lifts Vicki up to ride the Gauntlet/zipline to safety, an extra supporting hand can be seen around her waist as they cruise out of the frame.
Continuity mistake: After asking Joker if he's ever danced with the devil in the pale moonlight, Batman throws a right hand punch. However in the following shot Joker is seen getting hit with the left fist instead. (01:54:30)
Audio problem: When Vicki is kissing the Joker's arm near the end, the sound of her kissing is a fraction of a second off, enough to be noticeable.
Continuity mistake: When Vicki and Bruce take their plates to finish the supper in the kitchen, Vicki grabs her glass twice.
Continuity mistake: As Vicki waits at the museum cafeteria, you can see "Fluegelheim Museum" is printed on the menu on her table. But when she escapes with Batman, the sign at the front entrance of the building says "Flugelheim Museum". (01:00:30 - 01:07:20)
Continuity mistake: When the Joker is watching the pictures that his henchman gives him, he puts the one with Alexander Knox on the table. Then, he looks at Vicki's picture and there's now another picture on the table.
Continuity mistake: Vicky Vale's first name is V-I-C-K-I in the credits. On the cover of the magazine, it's spelled V-I-C-K-Y.
Visible crew/equipment: When Joker is being lifted by the helicopter at the end the lines from the safety harnesses that attach him to the ladder are briefly visible. (01:57:25)
Continuity mistake: When Batman collects the balloons' cables in his flying vehicle's anterior contraption, he gets 6 or 7 cables caught, but when he closes the scissor-like mechanism, there are only 5 visible cables. Also, when he collects them, they gather at the back of the mechanism, but when he closes it, they are neatly caught in small notches.
Continuity mistake: After electrocuting the guy at the end of the table in the crime-bosses scene, Joker (Jack Nicholson) clearly tries to put the scarf into his chest pocket but fails and lowers his hand while still holding it. But in the next shot the scarf is perfectly in place.
Continuity mistake: Whenever shots show the view looking down on the ground when Batman and Vicky are hanging from the cathedral, it only shows two spotlights shining upwards from the ground. In other shots just showing the upper part of the cathedral, there are three or four beams visible. Also, the movement of the beams from the ground and the ones actually on the actors don't correlate between shots.
Answer: He could have looked up her address in the phone book. Just before Bruce arrives at Vikki's apartment, Joker asks Bob the Goon for - a phone book. Also he could have been tailing Bruce and found her apartment that way, after all he does show up not long after Bruce does.
Alan Keddie