In Season 3 of Gilligan's Island, pop in the disc containing the episode "Gilligan's Personal Magnetism." Skip to the part where Gilligan has become invisible. Now go to the section where Mary Ann enters the Skipper and Gilligan's hut with a glass of coconut milk. When the invisible Gilligan starts to drink the milk, one can see a large rubber tube extending from Mary Ann's right sleeve and going to the bottom of the glass. This is how they got the milk to disappear! They sucked it through the tube.