Marshall becomes obsessed with saving the environment after seeing a documentary on garbage. Ted runs into The Captain. Barney admits he has feelings for a woman.

Barney declares February 13th a holiday for desperate women. Marshall receives a Valentine’s Day surprise from Lily. Zoey and Ted work on figuring out their relationship.

Barney gets emotional when he opens up to Honey about his life. Ted admits to having feelings for Zoey to the group.

While on a trip to Minnesota, Ted and Barney try anything to make Marshall laugh. Marshall runs into an old nemesis from high school.

Afraid they will never get pregnant, Lily and Marshall decide to see a specialist. Robin begins her new job.

Lily and Marshall receive shocking news that has a profound impact on the gang. Ted begins his duties as best man for an old friend’s wedding.

When Ted’s new friendship with Zoey tests the theory that single men and married women can’t be friends, he invites her husband, “The Captain,” to hang out with them. Meanwhile, Marshall and Robin decide to spend alone time together, and Barney and Lily possibly have a fight.

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.

Barney’s discovery of a Canadian kids show called Space Teens, that Robin appeared on as Robin Sparkles, leads the gang to get her to reach out to her co-star, Jessica Glitter.

When the gang goes to a black tie event at the Natural History Museum, Ted gets introduced to Zoey’s husband, The Captain.

When Zoey enrolls in Ted’s class, she manipulates his students into taking her side in the fight to save the building being torn down to make room for his project. Meanwhile, Marshall and Lily spot Robin marching in the Halloween parade of shame.

Marshall and Lily try to figure out how to conceive a baby with the gender of their choice; Robin’s perky new co-anchor irritates her.

Ted becomes conflicted after meeting an attractive woman who is passionate about saving the landmark building being torn down for his new project.

When the gang teases Robin about not being a real New Yorker, she sets out to prove them wrong by racing to catch a glimpse of Woody Allen.

Barney uses his best womanizing tactics to try to convince Ted to design the new GNB building; Robin drunk dials Don.

When Barney convinces the gang to help his mom move out of her home, they quickly learn that she has been very protective of Barney and lied to him about events throughout his life. Meanwhile, Ted gets upset when Robin oversells him to a blind date.

When Ted and Barney argue about who has “dibs” on a hot girl, Ted realizes that she is there with Cindy, a girl he previously dated who is also the roommate of his future wife. Meanwhile, Robin is heartbroken over Don, and Marshall can’t keep quiet about his desire to start a family.

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.

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.

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 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 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 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 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 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 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 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 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 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 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 Marshall picks up smoking again, it prompts Lily, Ted and Barney, ex-smokers all, to succumb as well. Meanwhile, Robin gets a new co-anchor at her show…

When a perfect girl finally shows up, the gang tries everything to help Ted, while Marshall takes action when he discovers a letter written by younger himself.

Barney freaks out when Marshall bequeaths a “slap bet” slap to Ted and Robin. Meanwhile, Lily’s estranged father shows up for Thanksgiving.

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

Lily comes up with a perfect plan to break up the relationship between Barney and Robin when they have a rough patch, but she needs help from Robin’s famous friend, Alan Thicke, in order to make it work.

Even though they do their best in order to be the perfect couple, Barney’s attitude of know-it-all lands him in trouble with Robin and they are forced to seek Marshall and Lily for advice.

Barney tries his best hoping to convince Robin into becoming an American citizen, while Ted and Marshall’s road trip takes an unexpected turn for the worst when Marshall invites Lily to come along.

Marshall and Lily want to hook up with Barney and Robin for double-dating and fun, but their desperate eagerness to please is a huge turn-off. Meanwhile, when a succession of girls come to his apartment and immediately fall asleep, Ted is bummed to learn he is a “Sexless Innkeeper” whose “dates” are only interested in a comfy place to crash

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.

Barney takes Marshall, and Robin to a strip club where they find a stripper who looks almost exactly like Lily. Meanwhile, Ted discovers he had been fixed up with the same woman, Jen seven years earlier.