Revealing mistake: When Skipper is blindfolded, as he rears back getting ready to sneeze, watch his right shoulder. You can see the line that pulls the blind off when he sneezes.
Revealing mistake: When Skipper is sneezing after Gilligan showered, he turns towards the wardrobe. As he sneezes, in a "blink and you miss it" moment, the line pulling up the bottom of the green cloth is momentarily visible, pulling from the upper right corner of the screen.
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.