Other mistake: On the police blimp, the scanner/radar screen in close-up has a single white circle, but in the wider angle it's two black circles, which are even hand-drawn and thus not perfect circles. (00:01:30)
The Man Who Killed Batman - S1-E49
Continuity mistake: Rupert Thorne's eyebrows are briefly white in one shot when he's talking to Sidney.
Continuity mistake: Scarecrow's pants turn red when he's on the catwalk turning on the pump machine.
Continuity mistake: Clayface has clay in the shape of the right hand on his chest when fighting Batman. A few seconds later it's suddenly in the shape of the left hand.
Other mistake: Two Face's lips on the left side are a shade of pink instead of dark red and his coin's all rough looking on the edge.
Continuity mistake: When Scarface's gang goes to steal the platinum from the ship and burn a hole in its hull, there is already a stack of platinum bars in their boat before they enter the ship.
Continuity mistake: For one frame during the final battle with the werewolf, the logo on Batman's chest is black and white instead of black and yellow. (00:17:55)
Continuity mistake: When Jervis Tetch is shown he's around 5'5 maybe with blue eyes and sandy white looking hair. Yet the day after his night out with Alice he's suddenly around Bruce Wayne's size with blond hair and his eyes are no longer blue.
Heart of Ice - S1-E3
Other mistake: When the children interrupt Summer Gleason's news report to play in the snow, the two police officers on the right are completely motionless for the entire 15-second shot. (00:02:10)
Other mistake: When Two-Face flips his coin in the air to decide whether or not to kill Rupert Thorne, Batman is surveying his surroundings, finding a box full of silver dollars and laboriously tossing the box into the air in order to make Two-Face lose sight of his coin. In the time it took Batman to do that, Two-Face's coin would have already landed back in his hand. (00:20:30)
Continuity mistake: When the chandelier falls on top of Rupert Thorne, the tommy gun he was holding falls into the bright half of Two-Face's hideout. Later when Two-Face grabs the gun, it is in the dark half of the hideout. (00:19:15 - 00:20:10)
Audio problem: When Rupert Thorne is saying "That file is here all right," his mouth is closed for the first four words. (00:18:10)
Other mistake: Several shots during Harvey Dent's fundraiser show characters in the crowd never blinking or moving a muscle. (00:07:10)
Continuity mistake: When Harvey Dent is walking away from the crime scene, Commissioner Gordon is on his right when next to the police van. Later when Rupert Thorne is watching the news report, Harvey is shown walking by the police van by himself. (00:05:40 - 00:07:00)
Continuity mistake: When Harvey Dent wakes up from his nightmare, his face is sweating profusely. A couple of shots later and there is no sweat to be seen on his face. (00:02:10)
Continuity mistake: Batgirl and Catwoman briefly gain pupils in one shot of them during the Stacked Deck fight, despite not having any throughout the episode. (04:00:39 - 04:41:24)
Continuity mistake: Batgirl's cape changes length throughout the episode. It goes from reaching her ankles to her hips.
Continuity mistake: The 10/6's on the Mad Hatter's mind control cards come and go throughout the episode.
Continuity mistake: By the time Batman gets to Ivy's garden, his cape and hood are blue, but turn to black a few seconds later.
Christmas With the Joker - S1-E38
Other mistake: Once Joker's back in his Arkham cell he should be wearing prison pants again like he was at the beginning of the episode. Yet he's still in his purple pants.
Answer: Because he stole a chemical from his lab.
But Batman knew that with it, Clayface could permanently retain his shape and Clayface desperately wanted to be Matt Hagen again. In a sense, Batman stopped Clayface from becoming human.