Star Wars Episode 4: A New Hope - Luke's Magic Cup Trick
When Luke enters his Aunt & Uncle's house for dinner or whatever, he picks up his drink cup. It switches over to another character, and when they switch back to Luke, he's holding it in the other hand. I know, it's stupid...
Look closely when the shot is from the end of the table, to Beru's left and Owen's right. There are two cups of the drink (blue milk?), one practically invisible because it's directly behind the other. Owen grabs his whil Luke has his in his hand.