Other mistake: Riddler says that his "universal wax solvent" can eat through anything. Which begs the question, just what is that vat he cooks the stuff up in made of? We see the wax burn through solid steel vault doors. So it also ought to be eating through the vat, the floor and the bedrock, and sizzling its way down to the Earth's core. (00:07:00)Jean G
Other mistake: Not only can Caesar Romero's moustache can be seen, but the line between the white makeup and his skin on his neck. Also, when Robin's face came out of the clay, his mask was almost around his mouth. A moment later, the mask is back in place. Later, his face, mask, and body is spotless.Movie Nut
Other mistake: Batman throws himself into acid. Counting on acid-proof suits, Batman comes out unscathed, but his ropes didn't get burned off until he dipped the back into the acid. Also, even though he covered his face a moment, he came out with his face exposed, and undamaged, when it should have been burned.Movie Nut
Other mistake: While Batman and Robin are ascending in the balloon, Robin picks up a chewed piece of gum, and stops the altimeter just before 20,000 feet. After that, Robin wondered how to get down. Beside Batman's head is the handle of the cord that would have started to let the air out, and started dropping them down.