My sister Emily has always been able to look at me, not say a word, and make me completely self-conscious. I will find her staring at me - on purpose - and despite my best efforts I completely unravel to the point that I eventually freak out and beg her to stop. She finds it hilarious, and used to do it quite frequently when we lived together.
Two years ago she had a baby boy...and HE CAN DO IT TOO. He has mastered the look. I don't know how, but he has got it down. I will say something silly to him, and the next thing I know he has me in a pool of jelly apologizing to the two year old because I said something so foolish!