Quote from Ted in Spoiler Alert
Ted: Okay! Let's hear it. What's wrong with Cathy? Barney: Are you kidding me, Ted? She's got a... Lily: Wait! You don't notice it? Ted: Notice what? Lily: Oh, he doesn't see it. If we point it out, we're gonna ruin her for him. As his friends, we'll just keep him in the dark. Barney: You're right. She's great, man. Robin: She's a keeper. Just... keep her somewhere else.