When the gang finds out that Barney and Robin are hesitant to define their relationship, Lily forces them to confront their biggest fear...becoming boyfriend/girlfriend. Meanwhile, Ted is anxious about teaching his first lecture at Columbia.
While on a blind date, Ted realizes this is actually his second first date with the same girl, and seven years later they still have nothing in common. Meanwhile, Barney takes Marshall out on the town, much to the dismay of Robin.
When Robin fears that Barney is cheating on her, she soon discovers that he is spending his evenings with Ted learning everything there is to know on how to date her.
When Lily and Marshall realize that Robin and Barney are the perfect double-date friends, they try too hard to impress and come on too strong, forcing Barney and Robin to try to break up with them.
While Barney tries to convince Robin to become an American citizen, Ted and Marshall's fabled road trip takes a wrong turn when Marshall invites Lily.
To prove that he and Robin are the perfect couple, Barney arrogantly gives relationship advice to Marshall, which results in a huge fight between Marshall and Lily.
After Barney and Robin hit a rough patch in their relationship, Lily devises the perfect plan to break them up, calling in help from Robin's famous friend, Alan Thicke.
When Robin and Barney break up, Barney pulls out all of his greatest tricks to get himself back into the dating scene.
Barney freaks out when Marshall bequeaths a "slap bet" slap to Ted and Robin. Meanwhile, Lily's estranged father shows up for Thanksgiving.
The gang tries to help Ted when the perfect girl is finally available, and Marshall takes action when he finds a letter written by his younger self.
The gang struggles to quit smoking while Robin clashes with her new jaded co-worker.
When Barney debates giving up wearing suits in order to land a hot bartender, his conflicted feelings lead to an amazingly awesome musical number. Meanwhile, Ted gets one step closer to meeting the future mother of his kids.
When Lily refuses to believe that Jenkins, Marshall's attractive female colleague, kissed him, Marshall insists Jenkins tell Lily what really happened. Meanwhile, Robin finds out that a drinking game has been made up about her.
When Barney is about to complete the perfect week - landing seven different girls in seven days - the gang roots him on in order to forget about their own miserable week.
When Lily and Marshall forget to fix up Ted on a blind date for Valentine's Day, they use one of Barney's many discarded girls to see if they may become Ted's future wife. Meanwhile, Robin's obnoxious colleague invites her to a party at his apartment.
When the gang tries to convince Ted that he is being strung along by Tiffany, they reflect about relationships where each of them has been in the same situation.
When Robin confesses that she is still angry with Barney for the way he handled their break-up, she enlists the help of Anita, a self-help author who plans to beat Barney at his own game.
When Ted ruins Lily's birthday dinner celebration by bringing a date, Lily goes to great lengths to keep her out of the traditional photo she takes every year of the gang.
When Marshall gets mugged, Lily decides she wants to get a gun for protection, so Marshall comes up with a convoluted story about the mugging to deter Lily from following through.
When Ted attends his mother's wedding, he is extremely disturbed by her overly affectionate relationship with her fiancé, which forces him to think about his own life and make an impulsive decision.
When Ted and Barney jeopardize Robin's new relationship by professing their love for her, Robin realizes that she is finally over them. Meanwhile, after spending a weekend sleeping in twin beds, Marshall and Lily decide to get twin beds at home.
When Ted, Marshall, Lily and Barney crash a highfalutin party at a swanky New York apartment, Ted gets the chance to mingle with the snooty guests and show off his intellectual side.
When Ted takes a date to see a new hit movie, "The Wedding Bride," he is shocked to learn the story is loosely based on his life, and that it was written by Tony, the man Stella left him for at the altar.
Marshall and Lily make a secret pact to start trying to have a baby if they ever finally see Barney's doppelganger. Meanwhile, Robin finally gets an offer for her dream job.
