Revealing mistake: Near the end of the episode, all the castaways are passed out cold when Lord Beasley finally catches his butterfly. Right after saying the line "That's the trouble with you Americans - you simply don't know how to hold your tea" as he's exiting off camera, Mrs. Howell starts to open her eyes slightly, but then quickly shuts them again. Perhaps she thought the cameras stopped rolling.
Revealing mistake: The footage of the assassin climbing up the drain pipe and leaping across the rooftop at the beginning of the episode is reused from the episode "A Room in the Basement." You can even see Drake already up on the roof from that episode, whereas there's only one person climbing in this one. (00:00:30 - 00:00:40)
Revealing mistake: At the very beginning of the episode, we see a hydrocharge being fired which causes an explosion in the sea. Then just a few shots later, another hydrocharge is fired and we see the same explosion - this is due to footage of one explosion being used twice.