How I Met Your Mother Season 2 Episode 18

(Lily and Marshall are lying on the couch making out)
Marshall: Should we, um, move this to the bedroom?
Lily: Why? Ted doesn't live here anymore. We can do it wherever we want.
Marshall: You know what else?
Lily: Hmm?
Marshall: We don't have to be quiet anymore. We can be as loud as we want.
(a few minutes later they're sitting at opposite ends of the couch)
Lily: Okay, I think we need to lay down some ground rules. Just because we can be loud doesn't mean we have to be loud. And although it might turn you on, you screaming, "I'm the best," doesn't do much for me.
Marshall: Well, it's a lot better than yelling, "Ted's not here," over and over again.
Lily: Well, at least what I said is true.
Marshall: Well, that was unnecessary.