Operation: Steam Heat - S2-E25
Revealing mistake: After Gilligan says his line about the earth swallowing them all up, an explosion rocks the area. Between the end of the line, and the rocking, there's a split second of blackness indicating a cut between the line and the action.
Operation: Steam Heat - S2-E25
Revealing mistake: When Gilligan and Ginger are in the cave at the volcano, you can see that the steam in the two passageway openings behind them is being shot in from jet nozzles.
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.