"I know more about you and I'm not picking out our matching homecoming dresses yet, so don't hold your breath." It wasn't as if he didn't also know a lot about, say, Oswald. Or Bruce Wayne. Any number of people at their school honestly. He noticed things, he liked to know things. Even if he doubted much of this would be overly relevant past high school. "Anyway, I assume to get someone pregnant, you'd have to do some kind of seduction first. Or just a lot of alcohol. I imagine that's how I happened."