Continuity mistake: When she was pulling Daggett up, Batgirl briefly gains pupils when she says "Catwoman, wait."
Continuity mistake: Harley's shoes are poorly drawn when she dances in Dr. Leland's office.
Continuity mistake: Catwoman/Selina gains and loses her pupils throughout the episode.
Continuity mistake: When Riddler burns his costume, he's wearing his purple gloves, but after throwing his green jacket into the fireplace, his gloves disappear entirely. (04:25:03 - 04:29:59)
Continuity mistake: The soles of Batgirl's boots change from light to dark blue throughout the episode.
Continuity mistake: Batgirl's boots gain and lose heels throughout the climax of the episode.
Continuity mistake: When we first meet Harley Quinn, her gloves are white before becoming their normal colors of black and red in the next shot.
Continuity mistake: Both of Harley's shoes are red as Batman holds her after rescuing her from falling.
Continuity mistake: During his introduction Scarface's scleras go from light yellow to white then back to light yellow.
Continuity mistake: When Poison Ivy is introduced in her trademark green costume, she's bare legged. Yet a few shots later, she's suddenly wearing green tights. While she's offscreen for a brief period, there's not enough time between the shots for her to have put them on.
Continuity mistake: The 10/6th on the Mad Hatter's mind control cards come and go throughout the episode. An example is when he first is shown holding them they're blank. Then when he decides to use them on his date with Alice they've suddenly got the 10/6th.
Continuity mistake: Scarecrow's shoes are light brown in most of the episode. Yet once he's back in his cell they're suddenly dark grey.
Continuity mistake: When The Joker's going down the garbage chute he's riding down on his butt yet somehow he's on his stomach after a shot of Batman is shown.
Continuity mistake: The Clock King slashes Batman's chest logo with his clock hand cane leaving it sliced up. A few shots later it's intact.
Continuity mistake: When Batman stops the countdown it reads as 1:45. When Scarecrow starts it back up it's suddenly 0:14.
The Cat and the Claw (1) - S1-E1
Continuity mistake: In the beginning when Catwoman lands, she's seen putting her whip away. In the next shot looking through the window, she's rolling up her whip.
Continuity mistake: Batman tears off the front of The Scarecrow's collar. Yet later in his hideout it's fine again.
Continuity mistake: Two-Face's left leg is blue here whereas it was normal in part 1 of his origin episode.
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.