When Maggie is talking to Ed in the bar, telling him what's wrong with men, she has one full shot glass in front of her. She tosses back the drink, emptying the glass. A few moments later, she empties the glass again, and the second she puts it down, it is full again.
Near the end in his office, when Joel drops his bag on the top of the bookshelves, the top shelf door drops down unintentionally. The door is shown alternatively open or closed for the remainder of the scene.