Ted: And you, you're mature and responsible now? Is it mature and responsible to go to your first big job interview in New York City and nail a total stranger? You've always been immature and irresponsible. You will always be immature and irresponsible. And I wouldn't cosign a library card for you, let alone a lease.
Heather: Barney and I didn't have sex.
Ted: Save it. Lily saw you.
Barney: Or did she?
[flashback to Barney undressing and Heather ruffling her hair in his office:]
Barney: [v.o.] You see, Ted, you had so little faith in Heather and me...
Heather: [v.o.] We decided to give you exactly what you expected of us. And I knew we could count on Lily to blab.
Lily: Oh, my God!