He creates alternate identities for the group so as to impress Jerry: Marshall is a playwright in an open marriage with Lily, while Robin and Ted are dating.
When they arrive at the house, Jerry produces a memento from their last day together when Barney was a kid: the "Legalize It" button they had gotten together, and expresses how much it meant to him over the intervening years.
Meanwhile, Marshall and Lily make a bet to see who can pick up five numbers from people at the club the fastest, with either winner getting to have sex in the bathroom.
Robin runs into an old crush of hers at the club; before she has a chance to ask him out, Ted claims to be dating her, to keep up the ruse for Jerry.
Robin points out Ted's hypocrisy as had only bought his red cowboy boots that day because another woman had told him he would look good in them.
[1] Henry Hanks of CNN.com's Marquee blog stated the episode was a "great example" of emotional arcs filling up the show.
[2] Vlada Gelman of Showtracker.com said the episode dropped clues about the wedding seen in "Big Days" and added speculation as to whether Robin or Nora is the "right girl".