The Bookworm Turns (1) - S1-E29
Other mistake: When Gordon falls into the water after being shot, the footage is in black and white, vs in color.
The Bookworm Turns (1) - S1-E29
Visible crew/equipment: When Printer's Devil contacts Bookworm headquarters, just as he messages "plot A washout" Bookworm walks over to the desk, and the white tape mark is visible on the rug where Lydia will stand. (00:07:25)
The Bookworm Turns (1) - S1-E29
Revealing mistake: At about the 6:40 mark into the episode, The Bookworm puts an explosive device in the Batmobile which is detected automatically. Batman pushes the auto eject to throw it out of the car. As the special effects prop explodes, you can see the rope it is hanging from as it swings to the side.
Answer: There wasn't one singular city used. It was shot in and around various locations in California, plus on a lot of sets and backlots. Ex. Some scenes were shot in LA, some in Pasadena, some in Santa Barbara, etc.
TedStixon