A student named Holly was sitting in class one day when the lecture took a turn for the worse. Bored stiff, Holly yawned so vigorously that her mouth got stuck wide open. Try as she might, she couldn't close it! She later learned that she'd dislocated her jaw. Watch what happened when she stepped into the emergency room. I don't know about you, but the sound of her jaw snapping back into place made me cringe. I'm just never going to yawn again. Thanks a lot, BBC!