Quote from Robin in The Leap
[flashback to Lily and Marshall talking to Robin at MacLaren's:] Robin: God, what am I going to do? Lily: I don't know. What are you going to do? Robin: I'm going to marry Barney in a big church wedding. We're going to move to some sleepy New Hampshire town and open a bed-and-breakfast. Marshall: Aw, really? Robin: No! It's Barney. I mean... it's Barney. But it's Barney. I got to tell him no. Lily: Oh, man, you're going to break his... Whatever it is that pumps that black sludge through his veins. Robin: Crap. You're right. The first time Barney expresses feelings for a girl and she rejects him? And not just any girl. I mean... It will destroy him.