Bob Denver's 4-year-old son, Patrick, played Gilligan in the chase scenes. Other techniques like forced perspective or double exposure had been used for years, but using Bob Denver's son was probably just fun as well as easier on the budget. In Casablanca (1942) little people were used next to a smaller prop plane. In Alien (1979) children were in space suits next to the giant alien pilot.
The giant chair in Gilligan's dream sequence looks exactly like the giant chair in The Incredible Shrinking Man, which was also directed by Jack Arnold.
The Lincoln green costume worn by Alan Hale Jr. as the giant is very similar to one worn by his father Alan Hale as Little John in The Adventures of Robin Hood (1938).
Gilligan's barber back home is named Sam.