I found an interesting (and I think heretofore undocumented) blooper in Walt Disney's 20,000 Leagues Under The Sea. At 3:00 minutes into the first scene (Opening Credits/Alarming Rumours) the character Billy gets up on stage to tell his tale about the sea monster. If you look above Billy's head, you see a sign for a hardware store. Above and behind that sign, you will also see 6 high tension electric power lines! In 1868 there were no electric power lines.