Ted and Barney discusses their viewpoints on knowing things about women. Barney thinks that the more you know the more likely you are to find a deal breaker. Ted wants to know the deal breakers right away, as Robin refuses to go to the mall to cover her secret.

Christmas approaches and Ted wrestles with whether to tell Robin about Barney's intentions involving Patrice, while Marshall and Lily get an early Yule gift, a night away from Marvin, but a case of separation anxiety strikes and threatens to ruin the evening.

After being forced into knocking back 5 shots, so he will stop thinking, Ted goes on a partying rampage. The next morning he wakes up with a woman in his bed, but he does not know who it is. So he turns to his friends to try and piece the night together and work out who the woman is in his bed.

After his relationship with Robin ends, Barney dusts off his "playbook" to help him back into the dating scene

The mother reveals how she met Ted and what she has been doing over the past eight years.

After Ted and Robin's first big fight, Barney tries to convince Ted that being an architect is an easy in to picking up chicks. Lily and Robin start following his trail after discovering that Ted hit it off with a girl named Anna shortly afterward.

Marshall awaits his bar exam results; Ted introduces his latest girlfriend to the gang, who all see the flaw that Ted has missed

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.

With everything going wrong on Lily and Marshall's wedding day, to everyone's surprise it's confirmed bachelor Barney who tries to fix it all.

It's still Marshall and Lily's big wedding day but now we're at the reception. Robin tries to tell a story but keeps getting interrupted. Barney tries his hardest to figure out Ted and Robin's secret.

Amid sharing stories with her about how members of the gang met each other, Ted's hot new girlfriend has a reaction to the meeting that gets her a high ranking on Barney's crazy scale.

Barney and Robin are afraid to break the news to Nora and Kevin that they cheated with each other and want to get back together, while Ted and Marshall get stoned together at a concert.

A mysterious tape arrives for Barney from one of his numerous ex-girlfriends, and the entire gang watches it. But, in order for them all to find out how she broke Barney's heart and made him into a suit-wearing bachelor, everyone must share their most embarrassing moment.

Ted tries to keep Robin from going on a camping trip so that she can spend time with him. Barney enlists the help of an old flame to perform a rain dance. At the same time Marshall finds out about Lily's interview for the fellowship in San Francisco.

Marshall tries to get used to being single in a world that is very coupled-oriented. Barney intended one-night-stand won't go away. Barney uses Lily to get out of his "horrifying" situation. Lily finds a place to stay.

Thinking that Bob Barker may be his father, Barney is overjoyed to be a contestant on The Price is Right. Marshall and Lily try sleeping apart prior to the wedding.

Lily and Marshall have their first Thanksgiving as a married couple; Barney is tortured by the slap bet countdown clock, worrying about when the slap will be dished out.

Ted pursues a woman named Stella, but only gets attention from her receptionist Abby.

The gang learns a new way to get their dates to sleep with them after Ted walks in on Robin's date sitting naked on the couch.

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 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.

Robin is nominated to receive an award for a news report and everyone needs a date to take to the show. Barney introduces Ted to Mary as a date that Ted can take to the show. Originally Ted is opposed to the idea of just trying to save face in front of Robin but when she shows up with a date he changes his mind. Robin asks Mary lots of questions, and Ted begins to really like Mary, despite her occupation.

Ted and Stella get engaged, but Ted soon learns that he doesn't know anything about her. Meanwhile, Barney confesses to Lily that he's in love with Robin.

Marshall claims that he had the best hamburger in the world during his first week in New York City, but he forgot where the burger joint is located. The gang then hits the streets of Manhattan to help him find it.

When Ted is packing his stuff for his move to New Jersey, he discovers that the gang was going to hold an intervention for his engagement to Stella and demands they hold it anyway.