When somebody tells you information about themselves and then forgets they did any such thing. You then use said information to impress them.
"A drunk girl at a bar told me she was a Virgo in some random conversation. I went out for a cig a while later and she followed. She asked me the same set of questions about my 'sign' as she had inside the bar. I said, 'let me guess, you're a virgo'. Her jaw dropped. An hour later I was getting a BJ in her car" - Zenitram
Groundhog Technique