Continuity mistake: After the shark bites Gilligan's paddle and he holds it up, the amount of wood between the handle's connection and the bite differs from shot to shot.
Revealing mistake: When the shark is attacking Gilligan's oar the second time, it stops completely for a couple of seconds.
Revealing mistake: As the shark goes by the floating bottle and towards the camera, the underwater rail the prop shark rides on is obvious.
Continuity mistake: While the castaways are standing around while their clothes dry, Mary Ann is not wearing any shoes. As the scene continues she is shown standing wearing black shoes. (00:05:00 - 00:06:00)
Other mistake: The Communal Hut is built in the clearing, and has a dirt floor. When Skipper and Gilligan check outside, it's floating in the lagoon. But that suggests it had a wooden floor.
Continuity mistake: As Mr. Howell tells his story, the table Ginger is on rocks to the point the canteen beside her falls off. A second later, she's drinking out of it.
Revealing mistake: The beam the Skipper wants Gilligan to work on is six feet, but if you look carefully, the beam is already pre-cut.
Voodoo Something to Me - S1-E4
Revealing mistake: While searching in the jungle, Gilligan slips and goes down a slope. As he gets toward the bottom, the plastic sheeting used to make the slide ripples.
Voodoo Something to Me - S1-E4
Continuity mistake: As the Professor comes up to Skipper and the girls, his left hand goes up to his face, but a second later it's his right hand on the bridge of his nose.
Good Night Sweet Skipper - S1-E5
Continuity mistake: When the Professor drops a couple of tranquilizer pills in the Skipper's cup, it's nearly filled to the rim. As he hides the bottle of pills, the liquid is a little lower.
Good Night Sweet Skipper - S1-E5
Revealing mistake: In the end scene, as Gilligan chases the bug, trying to quiet it, you can see the lines in the gourd where the hole will be after he hits Skipper with it.
Good Night Sweet Skipper - S1-E5
Revealing mistake: At the end, when Gilligan is holding to gourd up, chasing a fly, the lines of the cut out spot for the final gag are visible.
Visible crew/equipment: As Wrongway says "A couple more minutes, I could've been killed", the studio lighting is reflected on the left lens of his goggles.
Continuity mistake: The bill referred to by Lovey when the Skipper and Thurston are arguing changes from stage money to a real one dollar bill, and back between shots.
Visible crew/equipment: During the dream sequence, when Gilligan starts a showdown with Mr. Howell and the Professor, someone's face appears in the window in the background for a second, and it's none of the castaways - someone in the filming crew most likely.
Continuity mistake: In this episode, the damage to the boat is different than seen in "Two on a Raft." Also, there was a vessel number on the bow of the boat that is absent in this episode.
Other mistake: Where Gilligan is yelling to everyone "Don't get on the minnow, the glue won't hold!" you can see a pack of Chesterfield cigarettes sticking out of his left front pants pocket.
Revealing mistake: While they are at the front or side of the damaged boat, you can see that the dark windows above them are obviously painted on, rather poorly in some spots, and not real windows.
Continuity mistake: As the raft starts to sink, Lovey goes into the water on the back side of the raft. When the camera is in a close up of Mr. Howell, she's sitting beside him again. Then she's neck-deep in the water in the next wide shot.
Other mistake: As the girls are trying to land their catch, the Skipper comes by and starts to help. Although he was walking by, when he starts to help, his pants legs are already wet from previous takes.
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.