In the episode where Monica is upset about never getting to sleep with anyone again, or have a first kiss again because she is marrying Chandler, there is a scene where she is in the coffee shop talking to Phoebe. The scene has two angles, one where you can see Phoebe and Monica's hair and one where you see Monica. Watch her hair, in one angle it is partially over her shoulder, then in the next its all behind her shoulder then when she gets up, it is magically over her shoulder again. I know you can move your hair, but you see her hair the entire time so you know she doesn't do it. Just watch the episode, its easy to see.