While Barney prepares for his wedding to a mystery bride, he and Ted reminisce about Punchy's wedding, including when Marshall and Lily announced they were having a baby. Meanwhile, Robin considers telling Barney she has feelings for him.
Robin tries to date her therapist, Marshall thinks his boss has gone soft on environmentalism, Barney suspects that Nora may be lying about her age, and Ted takes his Intro to Architecture class on the worst field trip ever.
Ted agrees to go on a date without researching each other on the Internet beforehand, Barney urges Marshall and Lily to find out and reveal the gender of their child, and Kevin tries but fails to avoid passing judgment on the group.
Kevin's declaration that everybody marries their parents ruins Marshall and Lily's romantic evening, but will anything keep Barney from getting lucky with Nora? And will Kevin finally get fed up with Ted and Robin's close relationship?
Ted finds his long lost crush from a Halloween party 10 years ago, but will there be any chemistry? Meanwhile, Lily's "pregnancy brain" convinces her to move to the suburbs, and Barney finds out he's one-quarter Canadian.
The gang explains to Kevin the origins of the "No boogie-boarding" sign in front of MacLaren's, which has to do with hurricane Irene. Meanwhile, Barney negotiates with Marshall about how to get out of wearing the ducky tie.
After Robin tells Barney that she's pregnant with his child, she receives some shocking news from her doctor. Meanwhile, a neighborhood teen plays a trick on Marshall while he decorates his house with Christmas lights.
After celebrating New Year's Eve, Marshall visits his father's graveside to carry on their tradition of tailgating. Meanwhile, Barney and Ted open a bar called "Puzzles," and Robin is forced to fill in for an inebriated news anchor.
Kevin proposes to Robin, but will he take it back when Robin tells him she can't have children? Meanwhile, Barney and Ted try to score on the "drunk train" to Long Island, but something is surprisingly holding Barney back.
While Ted waits to find out whether Robin loves him back, he discovers that Marshall and Lily have been trying to influence him in opposite directions to win a bet. Meanwhile, Barney tries to find Marshall and Lily's sex tape.
Barney gets played and heart-broken over a stripper named "Karma," Robin becomes bored with her life on Long Island with Marshall and Lily, while Ted searches for a hobby to fill the empty space in Robin's old room.
As Ted, Marshall, and Barney get together for their annual viewing of the original Star Wars trilogy, Ted begins to question if he will ever end up where he wants to be - especially now that Barney and Quinn are getting serious.
Just as Ted starts to settle into his new apartment alone, Barney tries to entice him into going out every single night. Meanwhile, Lily has a naughty dream about someone other than Marshall, and Robin finally becomes a famous news anchor.
Barney tries to set Ted up on dates so that he can forget about Robin, while also plotting to get Quinn out of her stripping job. Meanwhile, Lily sends Marshall on a getaway so that he will stop stressing over the baby.
Ted makes a fateful phone call to his old girlfriend Victoria, Barney's magic trick gets him in trouble with airport security just as he's about to leave on a trip with Quinn, and Robin tries to take the perfect birth announcement photo.