Marshall: Fine! Okay, so Lily came down to the office to bring me my pants...
Barney: And why did she have to do that?
Marshall: Because I forgot my pants.
[flashback to Lily at the GNB office:]
Barney: Lily, what are you doing here?
Lily: Oh, I'm here to give Marshall something.
Barney: Ah. Here to give him something. Gotcha. Nice.
Lily: Yeah, but I'm in a hurry. Can I just give it to you?
Barney: Sure. Okay.
Lily: And then you'll give it to him?
Barney: Wait, oh, hey. Wait. I don't know about all that. I mean, yours would have to be really good.
Lily: What are you talking about?
Barney: What are you talking about?