Revealing mistake: When Anna and Hans are dancing in front of the lighthouse, we don't see the shadow of the railing or the ground they're standing on.
Revealing mistake: Barry is handed a file at his work. He starts reading it but the paper is totally blank. (00:12:35)
Revealing mistake: When Jerry and Tom are tripping Mr. Bigley into the trashcan, neither them nor Mr. Bigley cast a shadow. But Bigley did in the previous shot, where Tom and Jerry did not. (00:52:20)
Revealing mistake: As the gang is watching The Phantom on the security monitors, he turns around and takes off down a hall. The only lights in the hallway are suspended from the ceiling in the center. Yet the Phantom's shadow is cast to his right on the wall, when there are no lights to his left. (00:10:50)
Revealing mistake: Just after Superman and Supergirl have their talk about him going after Brainiac, it cuts to Lois at the Daily Planet on her laptop. There is a close up and you can see her fingers on the keyboard. She is typing really fast, but the animation shows her fingers just hitting the same 3 or 4 keys over and over again. (00:20:05)