And Then There Were None - S3-E13
Continuity mistake: Whenever one of the castaways falls in the trap and "disappears", there is complete silence when their name is called out, yet when the Skipper falls in (the last of the six), suddenly Gilligan hears all their voices shouting from down below.
Answer: Bob Denver answered this when he was on a talk show hosted by Pat Sajak. He said they were going to write into an episode where the castaways found all these clothes, but it got too complicated, so he said, they decided, "who cares, it's only a TV show," and forgot about it. So the writers and actors even asked this, they just never bothered to address it.