Ted: Can't believe your mom's not coming to the wedding.
Robin: Okay, seriously, I need to stop crying. Does anyone know how to turn this off? Is there, like, a button or something?
Barney: Want me to feel around for it? It's probably somewhere on your back. What? Trying to cheer you up.
Robin: I don't think that's possible at this point.
Barney: Challenge accepted.

Ted: Why are they at Barney's?
[flashback:]
Stuart: Hey, Barney. Just returning Ted's boots I borrowed for Halloween.
Barney: You were a cowboy?
Stuart: No, my wife was Wonder Woman. Can you believe Ted thinks a guy can get laid wearing these?
Barney: Challenge accepted.

Victoria: No, you were right, I have to leave a note. It's common courtesy.
Ted: Well, it's not gonna be possible with Andrea the Giant standing guard up there.
Victoria: Oh, right, Klaus's sister.
Ted: It's too bad Barney's not here. Man, he lives for bridesmaids.
Victoria: Right, but he's not. And it's not like he could seduce Uta over the phone.
[elsewhere:]
Barney: [on the phone] Challenge accepted! [to Quinn] Honey, it's not cheating if it's on the phone, right?
Quinn: Say what now?
Barney: Quinn's on board!

Barney: Nora, how you been?
Nora: Fine.
Barney: Look, I don't know why you would possibly say yes to this, but, would you want to grab a cup of coffee with me sometime? 20 minutes. I was such a jerk to you. You can spend the entire time calling me every dirty name in the book.
Nora: I speak four languages. I'm gonna need more than 20 minutes.
Barney: I'll call you. You look beautiful, by the way. And here I thought it was too late for sundresses.
Nora: It's never too late, Barney.
Barney: Challenge accepted.

[flashback:]
Lily: Congratulations. You win.
Barney: Win? No, I don't want to win. Keep playing. More challenges.
Lily: Fine, you want another challenge?
Barney: More challenges, more challenges.
Lily: Fine, here's your challenge. Go down to the pharmacy and buy some diapers.
Robin: And get me a samosa from the Indian place.
Barney: Sounds like an errand.
Lily: While picking up a girl.
Barney: Challenge accepted!

Marshall: Wait, we're not unpaused?
Lily: Not yet. Mama needs some Papa. But as soon as we're done having sex, we're having that fight.
Marshall: So we're not gonna fight... until after we're done having sex. Challenge accepted.

Arthur: The Captain pretty much paid for this entire shindig.
The Captain: Please, enjoy yourselves, have fun, but don't touch anything.
Marshall: Thank you, The Captain.
Barney: Challenge accepted.

Barney: Ted, there is not a single thing on here that you are too old to do. In fact, if you did everything on the Murtaugh List, I'd call that a pretty fun weekend.
Ted: Barney, you are not 18 anymore. If you did everything on that list, you would die. That wasn't a challenge.
Barney: Challenge accepted. In the next 24 hours, I'm going to do every single thing on this list. And after I do, you will TP the laser tag place with me.
Ted: And if you can't do it?
Barney: I will spend three hours listening to you talk about architecture.
Ted: You have got yourself a deal. Robin, will you do the honors?
Robin: A gentleman's agreement!
All: Huzzah!