Other mistake: At the end of the movie, when everybody wonders where they are, Gilligan holds up a piece of wood that says Minnow-1, making everybody realise they are back on the island. The name of the boat was known as the S.S. Minnow, and not Minnow-1.
Other mistake: When Gilligan wakes up and tells everybody his dream, he hums the theme song from the movie Jaws. Nobody left the island yet so there's no way he'd know about the movie or even the music to it.
Other mistake: In this movie, after being rescued, the Skipper tells Gilligan they missed the days of miniskirts and Gilligan asks "What are miniskirts?" (As if he's never heard of them). However in the original series, an episode mentioned miniskirts and Gilligan said he can wear "minipants" since Ginger could wear miniskirts. He already should have known what they were.
Suggested correction: The castaways had a radio which always gave them information on the outside world (since being shipwrecked). Although usually the Professor used it the most, Gilligan has been seen in the original series listening to it himself, so he could have heard about the movie (out 3 years before the rescue) while still on the island.
Except that the Professor said that the radio hasn't worked in over ten years so Gilligan humming the theme song to Jaws would be impossible and all other current events wouldn't be known to the others either as they are asking about Jimmy Carter, Gerald Ford and Ginger asking about Watergate thinking it's the last name of a person.