Ted and Robin discover that sex with each other solve their fights as roommates, which makes Barney very jealous and angry. Meanwhile, Marshall reveals that he's too embarrassed to use the office bathroom.
Ted and Barney get an opportunity to run their own bar during a historic blizzard, while Marshall and Lily try to defy the odds and continue one of their cherished traditions.
Robin needs to find a television job in seven days or else she loses her work visa, and Barney volunteers to come to her aid. Meanwhile, Ted, Marshall, and Lily consider cleaning up their resumes
The guys find out that Barney is pretending to have a wife and son to make his mother happy, but the charade is blown when Ted makes a move on Barney's "wife."
Ted meets with his ex-girlfriend from college--a girlfriend who cheated on him constantly and Marshall and Lily can't stand, and Marshall tells the story about how he forgot to bring his pants to work.
Ted becomes angry with Lily when he finds out that she has been sabotaging all his relationships that she did not approve of, including his relationship with Robin.
Barney and Marshall don't tell Ted that the plans for the building he has been working on have been scrapped, and the guys try to figure out which Canadian celebrity Robin slept with.
Barney tries to do all the items on Ted's "I'm too old for this stuff" list while Marshall's over-competitive side comes out when he coaches Lily's kindergarten basketball team.
Ted's plans to make his own design firm in his apartment hit a snag when his personal assistant begins sleeping with Robin, and Marshall tries to find a way to make himself indispensable at his workplace.
While Ted struggles with an unorthodox architecture project, Robin finds out that Barney is in love with her, and Marshall threatens to take a long-considered leap from the roof to a neighboring building.
As Ted begins his new career as a professor and is about to meet his future wife, Lily forces Barney and Robin to have "the talk" and define their new relationship.
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. Meanwhile, Ted gets a new nickname from Barney after an unsuccessful hook-up.
Despite their best efforts to be the perfect couple, Barney's know-it-all attitude gets him in trouble with Robin and they are forced to ask Marshall and Lily for relationship advice.
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 Barney hooks up with a woman Lily had been saving for Ted, she gets revenge by stealing his "playbook," which contains all the moves he uses to pick up women. But will Barney have the last laugh?
Maggie a girl next door Ted has wanted to date for years has suddenly broken up with her latest boyfriend, giving him and many other guys a chance to score with her.