When Marshall finds out he's the "reacher" in his relationship with Lily and not the "settler," he considers pursuing a sexy and cool female coworker. Meanwhile, Ted finds out Robin is a drinking game for his architecture students.
Barney runs into problems when he displays his cell phone number during the Super Bowl, Ted asks Marshall and Lily to arrange a marriage for him, and Robin thinks that her co-anchor has asked her out on a date.
After the guys discover that Robin deliberately got Barney hooked up with an incompatible female writer, they find out that that they didn't realize that Robin hasn't been handling their breakup very well.
Ted angers Lily when he brings a random date to her birthday party, so she is forced to remind him of all the other random women he has brought along to important functions, only to discover that they weren't "the one."
As Robin contemplates moving in with her new boyfriend Don, Ted and Barney both decide that they want her back. Meanwhile, Marshall and Lily think they've revolutionized modern marriage when they begin sleeping in separate beds.
Marshall and Lily think they've spotted Barney's doppelganger, which means that they can start trying to have a baby, but it's really Barney in disguise. Meanwhile, Ted goes blonde and Robin considers taking an anchor job in Chicago.
Ted musters up the courage to talk to a girl at the bar, but then discovers she's there with one of his exes. Meanwhile, Lily is mad at Marshall because he told his dad they're trying to have a baby, and Robin lets herself go.
When Ted declines Barney's offer to design the new GNB building, Barney ties to woo him by using all of his best womanizing tactics. Meanwhile, Robin is still not over her relationship with Don and drunk dials him.
Is Ted having second thoughts about designing GNB's new skyscraper because it would tear down a landmark, or because he's trying to impress a woman? Meanwhile, Lily shares a secret about Robin's new boyfriend with Marshall.
Marshall takes steps to make sure that he and Lily have a baby boy, but Lily has other ideas. Meanwhile, when Ted begins dating Robin's co-anchor, Barney is inspired to use baby talk to pick up women, and Robin feels betrayed.
Marshall struggles to fire an incompetent employee, everyone tries to figure out whom Robin slept with Halloween night, and Zoey, the GNB skyscraper protester, finds a way to turn Ted's class against him.
Ted and Zoey's feud continues during a fundraiser at the Museum of Natural History. Meanwhile, Marshall confesses to Lily that he enjoys his job at GNB, and a prank by Barney and Robin may lead Barney to his real father.
While Barney finds a new video from Robin's Canadian teen star past, Lily fears that a baby could come between her friendship with Robin. Meanwhile, Ted's obnoxious old friend, "Punchy," comes from Cleveland for a visit.
When Ted leaves the bar early to prepare a Thanksgiving feast for his friends, the gang winds up partying all night with The Blitz, an old friend from college who has bad luck. As a result, Ted is forced to spend Thanksgiving with Zoey.
Ted goes on a boating trip with Zoey's husband, "The Captain." Menawhile, Barney's "Mermaid Theory" prevents Marshal from having a nice dinner with Robin, and the narrator tries to recall the details of a fight between Lily and Barney.
Barney and Robin contemplate drastic positive changes in their lives when Marshall and Lily announce that Lily is pregnant, but renege on their promises when Marshall and Lily tell them that it was a false positive.