Challenge Accepted

With the Arcadian, Barney and Ted argue who is going to press the button to blow up the building.

Ted mentions that he ran into his ex-girlfriend Zoey after breaking up and she asked to get coffee, which Robin and Barney say is a signal that she wants to get back together.

Marshall has a business meeting with a prospective employer and has figured out the time when he will begin vomiting.

We bookended the season with this song ["Ballad of Sir Frankie Crisp (Let It Roll)" by George Harrison], which was the first time it was hinted at that the place where Ted ultimately meets 'The Mother' was at a wedding.

"[3] This episode was shot with extra security because of the two major revelations at the end: Lily being pregnant and Barney being the groom at the future wedding.