This didn't cheer me up - bent over in a shop today to tie up my shoelace, got back up and was faced with someone standing there, staring at me, which made me jump. Was just about to start on the defensive, when I realised it was a ruddy mannequin. I felt a little bit stupid.
The best way to cheer up a sales assistant is to ask for the winning lottery numbers when asked if there's anything else they can do to help, because they never, absolutely NEVER hear that in their day!