I once heard Mark Hamill talk about STAR WARS at a panel, and he said during A New Hope they shot the film out of order, so he was extremely particular about the continuity of the movie. While filming, he realized in the previous scene they shot much earlier they were just in the wet garbage compactor, but now, moments later, his hair would be dry. So he leaned over to Harrison Ford, worried about how his hair should actually be wet, stating mistakes like that would take people completely out of the movie. Harrison Ford turned to him and dryly said, "Look, kid, if they're watching this movie and looking at your hair we're all in big trouble."