Other mistake: Mary Ann comes up to the Skipper while he's learning to juggle. If you look closely, the coconut bounces on the ground a couple of inches from his left foot. When Gilligan approaches, the coconut bounces off the bottom shelf. And in both times, the Skipper reacted in pain.
Other mistake: When Mrs. Howell looks at the lion in the mirror, the image is not reversed as it should be when the camera looks directly at the lion.
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.