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.

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.

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

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.

The gang works together to plan a legendary bachelor party for Barney.

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

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 -- and a pineapple. The gang tries to piece together the night and figure out who the woman is in his bed.

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.

Ted finds a new woman at the wedding. They want to remember the evening so they don't exchange last names or numbers; but Ted takes a big fall when he tries to find out her name.

Ted is conflicted when Victoria approaches him on her wedding day and asks him to elope. Meanwhile, Barney and Quinn are arrested by airport security while on the way to Hawaii when Barney refuses to open a box they are travelling with.

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.

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

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.

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.

Robin receives bad news and decides to hide it from the gang. Marshall hangs Christmas decorations in his house in the suburbs with some help from his neighbor.

As the gang prepares to go to Robin and Barney's wedding, Ted invites Lily to see the house he's finally finished fixing up. Meanwhile, Robin and Barney's night of relaxation is ruined by an obnoxious couple, and Marshall takes the baby on a last-minute trip to Minnesota to see his family.

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.

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.

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.

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.

Ted, Marshall and Barney embark on another "trilogy time", where they get together every three years to watch the "Star Wars" trilogy and envision what their lives will be like in another three years. Meanwhile Barney and Quinn move in together.

Marshall goes on his first real date post-breakup with Lily. Not only do Ted and Barney try to warn him that this girl has got the crazy eyes, but Lily decides to do everything she can to find out about this her and break them up. Also, Barney gets a new name.

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.

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 faces having to wear Marshall's ducky tie if he loses a bet with him. Meanwhile, Ted hopes to apologize to an ex for cheating on her.

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

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.

Robin attends Lily's bridal shower and finds the gift that she brought is out of place. Barney hires a stripper for Marshall's bachelor party.

When Lily goes into labor, Ted and Robin distract her by telling her stories while Marshall hurries back from Atlantic City.

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

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.

Robin takes steps to have Patrice fired from WWN, while Marshall puts a jinx on Barney. Later, Ted invites his architecture professor to the dedication of the GNB building, and Marshall and Lily bump into an oddball acquaintance from college.

Ted is in a car accident that prompts Marshall to talk about miracles. Everyone flashbacks to prior moments in their lives.

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.

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.

With only a half an hour left before the wedding, Robin and Barney panic; Lily and Marshall rewrite their wedding vows.

Barney meets his father and is shocked by the differences in their lives. The rest of the gang learn their "gaps"; knowledge they should have by now, but don't.

When Robin breaks up with Kevin, Ted confesses his feelings to her. Meanwhile, Barney is on a mission to find something private of Marshall and Lily's.

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.

Robin and Barney bond when they intervene in Ted's relationship, and Marshall and Lily watch a ticking clock as he fears that he soon will be the victim of food poisoning.

Ted is trying to keep his architecture firm afloat by doing an all-nighter, but Marshall tries to lure him to the roof for a surprise 31st birthday party, on the fourth season finale.

Ted breaks one of Barney and Marshall's relationship rules, texting a woman he recently met, so the pair play a joke on Ted by pretending to be the woman.

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.

The gang tries to break up Barney and Quinn after learning they plan on moving in together, leaving Robin and Ted to fight over who deserves to sublet her apartment.

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.

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.

Lily and Marshall try to continue their airport reunion tradition. Barney and Ted offer to keep MacLaren's open during a blizzard so they can meet up with some college girls.

When Ted's best friend Marshall proposes to his girlfriend, Lily, Ted realizes he'd better get a move on if he hopes to find true love. Ted soon meets Robin in a neighborhood bar, immediately becomes smitten and scores a first date. But when Ted can hardly wait to see her again, his eagerness threatens to scare her away.

A man at the wedding intentionally stirs up trouble; Marshall finally arrives at the Farhampton Inn.

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.

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 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.

While the gang reminisces about Hurricane Irene, Barney tries to cut a deal with Marshall and Lily to get out of wearing the Ducky Tie.

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.

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.

Barney's efforts to hook up with women are being thwarted by a mysterious woman from his past. Barney and the gang must sift though his many past flings in an attempt to find out who she is.

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.

Lily gets asked to play in an off-off-off-off-broadway play, and the gang shows up to support her. Ted and Robin get hung up on what each kept from their past relationships. Barney performs his own play to prove a point to Lily.

Ted's parents visit New York for their anniversary and he learns a family secret. Robin worries that they won't like her. Lily and Marshall try to adjust to the new format of their relationship now that they are no longer together.

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 are having a baby. Meanwhile, Robin considers telling Barney she has feelings for him.

Marshall tries to get Marvin to sleep by reciting rhyming bedtime stories.

In an attempt to deliver a devastating final slap to Barney, Marshall explains how he mastered the Slap of A Million Exploding Suns.

Ted finally finishes telling his kids the story of how he met their mother.

Barney concocts a plan when his father arrives at the hotel; Ted thinks he is being framed when a wedding-related duty gets messed up.

Robin and Lily have a fight on the morning of the wedding; Barney can't decide what suit to wear; the gang watches a movie that Ted didn't want them to see.

Marshall and Barney lie to keep Ted from finding out the headquarters he'd been hired to design for GNB has been cancelled.

Marshall and Lily are less than thrilled when they hear that Ted's college girlfriend (Laura Prepon) has moved to New York.

When Barney and Abby realize that they have one thing in common - their mutual hatred of Ted - the "couple" decides to go to the bar to flaunt their new relationship in Ted's face.

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.

Ted finally meets his mystery girl in the Slutty Pumpkin costume. Meanwhile, Barney learns he is part Canadian, and Lily has pregnancy brain.

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.

Barney and Ted compete for a girl. Robin is dating someone new.

Barney is upset after Robin wins James's wedding ring during the poker game, and Ted argues with Marshall and Lily over whether he gave them a wedding gift.

When Stella's babysitter cancels, a night out turns into the gang hanging out at her place, and Ted talks up New Jersey... until he learns Stella wants him to move there after marriage.

Lily asks for her father's help when she and Marshall decide to throw a housewarming party. Marshall's boss gets under Ted's skin and the two nearly come to blows, and Barney puts the moves on a wacky divorcée.

Robin desperately tries to locate the item that she buried in Central Park years earlier to wear as her "Something Old" for the wedding. Meanwhile, Marshall and Lily ask Ted to help them pack for Italy, and Barney invites Robin's father to play Laser Tag in order to bond with him.

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 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.

Barney creates a holiday to celebrate not being a father. Meanwhile, Lily and Marshall are considering having a baby, but Lily first wants advice from Ted and Robin.

When Lily and Marshall have trouble finding a nanny, they learn it's because of an elaborate scheme Barney came up with to meet girls. Meanwhile, Robin and Ted butt heads over who has a more serious relationship.

Barney begs Ted to continue seeing his much younger, much wilder girlfriend, even though Ted has nothing in common with her. Meanwhile, Robin must adjust to the power of the bling.

Ted finally finishes telling his kids the story of how he met their mother.

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.

When a matchmaker with a 100% success rate turns Ted away because he is not compatible with any of the available women in her database, he is still determined that he is going to find his match. Meanwhile, Marshall and Lily are obsessed with ridding their apartment of a critter.

Ted is trying to find a new job, and when an old acquaintance tries to help nothing goes as planned. Barney tries to smooth talk his way out of a ticket.

Ted goes out on his own as an architect and hires an intern to help get things started, but the intern gets a little too close to others in the gang.

When Daphne sends a troubling text message to Lily, Marshall enlists the gang's help to remove the message while enforcing the "No Questions Asked" rule.

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.

As the season of break-ups continues, Ted and Victoria must choose the next step in their long and complicated relationship. Meanwhile, Robin worries about Barney when he chooses a dog to be his wingman.

Marshall decides to step in after seeing his boss's approach to settling with a million dollar company. Ted's class trip isn't what he envisioned.

When Barney loses his way with women, he hopes a trip to the Victoria's Secret Fall Fashion Show will help him regain his form.

Marshall takes on his old friend/new nemesis Brad in the biggest case of his career. Meanwhile, the gang reminisces about their own run-ins with the law, leading to a debate over who was the biggest delinquent as a teenager.

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...

Ted is reluctant to break up with his crazy girlfriend Jeanette. Meanwhile, Robin becomes attached to Marvin after finally holding him for the first time.

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

Lily and Barney react badly when Marshall finally quits his job at Goliath National Bank to take a volunteer position at an environmental organization. Meanwhile, Ted and Zoey's opposing positions on the future of the Arcadia come between them.

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 Barney designs an extensive pre-nup, the guys take note and propose their own relationship amendments to their significant others. Meanwhile, Quinn is outraged and draws up a pre-nup of her own, which causes friction between the sexes.

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.

Ted and Barney pretend to be visitors to New York City to pick up women. Robin is still dating Gael.

When Ted finds himself with three prospects to be his date for the wedding weekend, he chooses poorly. Meanwhile, Barney and Robin have a confrontation with their minister, and Marshall learns more about his driving companion, Daphne.

Lily and Marshall officially move to the suburbs and realize that Lily's bossy father refuses to move out of their house. Meanwhile, the gang adjusts to them moving by going to a strip club.

When The Captain asks Lily to move to Rome for a year as his art consultant, she fears that Marshall will resent her. Meanwhile, Ted and Barney become obsessed with a girl who is hiding her amazing body under a puffy coat.

When Robin and Loretta's conflict escalates, Barney is caught in the middle. Meanwhile, Marshall and Daphne deal with a stowaway on their road trip, and Ted and Cassie try to enjoy a trip to a lighthouse.

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 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.

Robin and Ted reminisce about past relationships as they search for a drunken Barney on the day of the wedding; Lily and Marshall come to a resolution; Barney befriends two men who are eager to meet women.

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.

Marshall recommends his old law school classmate Brad for a job at his firm, but the interview goes awry, leaving Marshall to do damage control with his boss. Meanwhile, Robin helps negotiate Barney's return to the strip club circuit.

Marshall interns at the corporation where Barney works and Lily finds that he is becoming a shallow jerk as he tries to fit in with his crude fratty coworkers. Meanwhile, Ted feels guilty when he receives several gifts from Victoria (Erika Singh) while he hasn't sent her anything.

When Robin is hesitant to break up with Nick, Barney takes matters into his own hands. Meanwhile, Lily and Marshall are desperate for some private time.

Robin is determined to get Barney back no matter what it takes. Meanwhile, Ted fills in as Marvin's Nanny, leading Marshall and Lily to realize that Ted is using baby Marvin to replace his other baby, the GNB building.

When Ted is constantly insulted by his former boss, who is now working for him on a project, he is told to fire the man, but he finds that a hard thing to do. Meanwhile, Barney offers Lily a lot of money to paint a nude portrait of him.

Marshall and Lily drag the gang to Atlantic City to elope, and their quest to overcome the three-day wait for a marriage license crosses them with some Chinese gamblers, a ship captain, and a sexy novelty shirt.

Marshall and Lily's plan to buy an apartment is hampered by mistakes and Lily's hidden debt.

While Barney works through his anger at Ted after finding out he still has feelings for Robin, Marshall Skypes in to act as a judge and help settle their dispute. Meanwhile, Lily realizes she is Robin's only girlfriend.

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

When Ted receives an unexpected call from The Captain, the gang reminisced about their last awkward encounter with him.

Ted agrees to let Barney spice up his love life, and ends up on a crazy adventure of flying to Philadelphia, encountering the law, and visiting the Liberty Bell.

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.

Ted's outlook on his continuing search for love is altered when he rediscovers a shirt that has not seen daylight in years. Meanwhile, Barney amuses himself by coaxing Robin into sacrificing her job by saying completely outlandish things on air live for a cash reward.

Ted makes his yearly pilgrimage to the rooftop Halloween party in search of a girl dressed as a pumpkin who he met years ago. Meanwhile, Robin struggles her new boyfriend because of her independent ways.