Barney: Ooh, why, Lily Aldrin, you saucy little harlot. Could it be that before Marshall took a swim, someone else tested the water?
Marshall: No. Nobody else tested the water, right? Scooter?
Barney: Who's Scooter?
Lily: My high school boyfriend, who I did not have sex with.
Marshall: I... I can't believe this. We're Marshall and Lily, when people see us, they say, "Oh, look at them, they've only had sex with each other."
Barney: No, Marshall, they say, [sad voice] "Oh, look at them, they've only had sex with each other."
Marshall: But now that's not true anymore, now you've had sex with twice as many people as I have. I knew that you were too good at it.