Barney: Then why did she pretend to ridicule it as an idiotic idea?
Lily: Because it is an idiotic idea. If Robin actually was planning a surprise, don't you think she would tell her maid of honor?
Barney: She didn't tell you 'cause you can keep a secret the way my dentist keeps his car keys. You don't know him, but he's lost them... Like, twice. Actually, just once, and... That time they were in his other pocket.