Continuity mistake: When the SS Minnow is shown beached on the deserted island, it's seen leaning on its left. At the ending credits, the Minnow is shown completely upright.
Continuity mistake: When they are listening to the radio report describing the lost boat, the professor goes from standing up to sitting down between shots.
Continuity mistake: At the beginning of the episode when everyone is listening to the radio the professor is shown standing up and in the next shot is sitting down. (00:02:50)
Continuity mistake: As they struggle with the sail, Skipper's hat is backwards. After a shot of the shark, his hat's on right as he tosses the sail.
Continuity mistake: After the shark bites off the rest of the paddle, leaving the handle, Gilligan hesitates a second, sees no paddle, and begins swatting at the shark. A moment later, in the closeup, he's paddling, hears the bite again, and pulls the handle up, showing the paddle is gone.
Continuity mistake: As the rock that triggers the trap is pulled, the vine used slides completely off it. In the wide shot, the vine is securely around the trigger rock.
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.
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)
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.
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.
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.
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.
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.
Continuity mistake: After the earthquake the skipper is holding the idol with both hands. The shot changes and only one hand is holding the idol.
Gilligan Meets Jungle Boy - S1-E20
Continuity mistake: When the Skipper squeezes Gilligan to get rid of the helium, in one shot the Skipper's hat is on, and in the other it is not.
St. Gilligan and the Dragon - S1-E21
Continuity mistake: As the women are packing up to move out, Mr. Howell says he and Lovey have been married for nineteen years. As the men are trying to get to sleep, he says they were married twenty-two years.
Big Man on a Little Stick - S1-E22
Continuity mistake: As the Professor sends Duke off, he gives the island's position as 110° Latitude, 10° Longitude. In "X Marks the Spot" (S1: E: 19), the position is given as 140° Latitude, 10° Longitude.
Continuity mistake: At the end after Gilligan pretends to throw away the Eye of the Idol, everyone gets up to look for it. As the Professor gets up, Gilligan gestures to him. In the next second, his arms are on the table.
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.