About this scene
Bookstore fiction section, late afternoon. She's a blonde in a sweater and jeans, holding a hardcover novel. The flash happens at the next aisle over. She drops the book once. She picks it up, holds it for two seconds, then drops it again. Both drops happen inside ten seconds. She crouches the second time to retrieve it and stays crouched for several seconds longer than she needs to. By the time she stands back up her face is fully red.
What to watch for
The double drop is the comedic structure. The first one is involuntary. The second one is also involuntary, and that's the part that's surprising. Most people recover after the first surprise. She does not. Watch her hands when she picks the book up the second time. They are visibly unsteady. The crouch lasts about six seconds longer than it physically needs to, which is just enough time for her to compose her face before standing back up.