My now wife's younger sister visited her in college. I was over there and this other dude I didn't care for stopped by to chat. Upon seeing the sister, he started flirting. He was 24. The sister looked much older than her age. As he began flirting, I thought to speak up, but as I mentioned I didn't care for this guy, so I let him flirt away for about 15 minutes. When I felt he was close to asking her out, I interjected, "Megan, remind me when you turn 14?"

Flawless victory