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
Continuity mistake: In the wide shot of Batman hanging upside down in Mr. Freeze's lair, his face is blank and the bat outline from his chest emblem is missing. (00:14:10)
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: 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.
Continuity mistake: Bruce's robe goes from a light purple to mint blue while he's talking to Alfred at the end of the episode.
Character mistake: The Scarecrow's thugs flee as his water pump machine explodes, yet he seems to have stuck around long enough to be affected by his own toxin.
Continuity mistake: Both Selina's, once she's been mutated, and Tygrus' noses change color. Hers goes black briefly when she finds Batman in the forest and Tygrus' turns grey briefly as Dr Dorian scolds him.
Continuity mistake: When Clay-Face makes things like crab claws they're red. Yet later on when he fights Batman again in the TV station they're light brown.
Continuity mistake: The clay used to bind Germs goes from a creamy light brown to dark brown.
Continuity mistake: Scarecrow's boots start out dark red then they're light brown later in the episode.
I've Got Batman in My Basement - S1-E20
Other mistake: Toss a brick into a pile of empty boxes, and they won't fly around like it is shown. The heavy brick will sink into whatever hits and possibly other boxes will be affected; here the brick does not deform the box it hits and every single cardboard acts like bouncy balls. (00:13:30)
Answer: She escaped off-screen and created a copy of herself to fool everyone.