Character mistake: Despite being a Greek mythology buff Maxie Zeus says "Vulcan" when he meant "Hephaestus" the Greek god of fire and the forge when he first spoke with Batman.
Character mistake: Nick asks Janette if she's ever turned anyone else into a vampire - an odd question, considering the fact that he already knows she has. He was there when she brought the baroness across in the 18th Century flashback sequence for "If Looks Could Kill." It's even odder that Janette tells him she's never done it, since she knows that Nick knows she has. Apparently, the only one not in the know here was the scriptwriter.
The Tale of the Manaha - S5-E7
Character mistake: Near the beginning as the leader is about to set off with the boys, he says, "About face!" and turns to the left, and the boys follow suit. But "About face" means to turn 180°. He should have said "Left face" to get them to turn 90° to the left. (00:04:25)