Continuity mistake: Just before Batman takes his mask off at the end, the black makeup around his eyes vanishes while the mask is still on. (01:48:20)
Continuity mistake: In Schreck's department store, when Catwoman is doing her cartwheels, her heels collapse. (00:53:40)
Continuity mistake: When the Penguin is looking out of the barred sewer hole, from an inside shot we see the penguin holding two bars, and in between the bars he is holding are two bars. In the next shot, there are four bars in between. (00:06:05)
Continuity mistake: Catwoman's lipstick smears down onto her chin when she puts The Penguin's bird in her mouth, yet in the shot just before she gives herself a "bath", the lipstick momentarily is gone. (01:03:20)
Continuity mistake: When Selina returns home from work she takes milk out of the fridge and pours her cat some, leaving the carton on the worktop. She then runs to work, and when she returns after being changed to 'catwoman', the milk has vanished from the worktop. The dishes also move and plant pots appear on the window sill. (00:22:50 - 00:28:45)
Continuity mistake: When Selina retrieves her papers from the floor, she places them in a disorderly pile beside the clown. In the shot when she zaps the clown with the taser, the papers have changed position and are stacked neatly. (00:15:55)
Revealing mistake: Outline of the broken piece Batman will yank out of the wall to save Selina is visible before he makes it. (00:15:15)
Continuity mistake: The rubble and debris from the piece of wall which Batman tore from the wall, which lies beside the clown, differs between shots, and so does the clowns position. (00:15:50)
Continuity mistake: When Selina becomes enraged and trashes her apartment, she grabs a frying pan off of the oven hob, which was not there previously, when she entered her apartment. (00:28:40)
Revealing mistake: When The Penguin shoots the clown who says "Killing sleeping children...", as the clown falls back to the floor, you can clearly see he falls on a wrinkled, soft mat which has unsuccessfully tried to be disguised. (01:29:30)
Visible crew/equipment: When the Penguin dies and the penguins slide him into the water you can see the slide-board he was laying on slip out ahead of him under the water. It is also very clear that the penguins aren't even touching him as they pull him into the water. (01:53:00)
Continuity mistake: Max's big outer coat and his patterned scarf suddenly disappear between shots, when he leads the Penguin over to his image consultants. (00:48:45)
Continuity mistake: When Max is walking up to Selina from behind, we see her flipping through files, and she puts the paper back down into the drawer. In the very next closeup she's suddenly looking at another file. (00:24:25)
Continuity mistake: After Max Schrek throws some of the presents out to the crowd, when it cuts back, between shots a large green present on the top of the pile vanishes. (00:09:55)
Continuity mistake: During shots, before the shot of the two cats coming through the window and onto the table, the items on the table (lamp, snowglobe, glowing santa, etc.) change positions. (00:30:15)
Continuity mistake: When Selina arrives back home after being pushed out the window, she presses her answering machine button and brings her arm to her side. In the next shot her hand is on the machine again. (00:29:05)
Continuity mistake: When the joker henchman busts the door and lifts up a flaming stick to blow at a pile of teddys, the angle in which he holds the stick differs through consecutive shots. (00:13:40)
Continuity mistake: The yellow bottles of fish food jump from the radio to the fridge, from when Selina arrives home the first time, goes off back to work, then returns back home the second time. (00:22:30 - 00:28:50)
Continuity mistake: When the Penguin is first talking to Max, about him helping him emerge from the sewers, he spits as he speaks, and black spit covers his chin. The spit disappears when he begins to show Max the toxic waste, then reappears and vanishes again. (00:20:00)
Continuity mistake: As Selina is about to make her cat suit, she grabs a pair of blue handled scissors, yet in the next shot they're pink. (00:31:05)
Answer: It isn't. If you look at when he dies you will see that he has cuts on his face that are bleeding red. The blue liquid is more like a bile, probably similar to saliva.