Barney: Oh, this one looks interesting.
[flashback to Marshall holding a video camera in his bedroom with Lily:]
Marshall: Lily, I thought you said you wanted to. It was your idea. I starved myself for a week to get camera-ready.
Lily: You had a bear claw for breakfast.
Marshall: Yeah, a bear claw.
Lily: I changed my mind. I just don't want Barney to see us doing it.
Marshall: Barney is never gonna see this.
Lily: Oh, come on. It's Barney. Eventually, somehow he's gonna see it.
Marshall: Want to bet?
[present:]
Barney: So there really is a sex tape. [runs out]