The laughs continue in the fifth season of HOW I MET YOUR MOTHER! It all started when Ted's best friend, Marshall, dropped the bombshell that he was going to propose to his long-time girlfriend, and now wife, Lily, a kindergarten teacher. At that moment, Ted realized that he had better get a move on if he too hopes to find true love. Helping him in his quest is Barney, a friend with endless, sometimes outrageous opinions, a penchant for suits and a foolproof way to meet women. When Ted met Robin, it was love at first sight, but when things didn't work out, Ted realized destiny must have something else in store. The series is narrated through flashbacks from the future.
After sharing a kiss at the beginning of the summer, Robin and Barney are unsure how to handle their mutual attraction. After some consideration they tell the gang they have decided to remain just friends, but secretly continue seeing each other. They are able to get away with their secret romance for a couple months, but are discovered when Ted, Marshall and Lily walk in on them together. They explain to the gang that they are happy with their casual relationship, and didn’t want to complicate it by defining it. This is unacceptable to Lily, who pressures them to label their situation, and ultimately locks them in Robin’s room to force them to address it. Meanwhile, Ted is anxious about his first days as a professor at Columbia, which is made worse when he shows up at the wrong class and starts his lecture.
Mid way through a blind date Ted discovers he had been fixed up with the same woman seven years earlier. The woman, Jen, realizes the same thing, but instead of giving up on the rest of the date, they decided to let it play out so they can see where it went wrong the last time. As they go about replicating their last date, Jen and Ted help each other understand what turned them off about the other person, and come to realizes that a few tweaks to the date could have ended up with them getting married. Meanwhile, Barney takes Marshall to a strip club where they find a stripper who looks almost exactly like Lily, and Marshall admits to Barney that he has problems fantasizing about anyone but Lily.
Robin and Barney are now official but Barney has been having trouble adjusting from his bachelor ways. Off of Barney’s actions, Robin begins to question whether or not he is capable of being in a relationship. Ted, upon hearing Robin’s concerns, takes it upon himself to fill-in Barney. Barney is scared Robin will leave him so begins trying extra hard to be a good boyfriend – so hard that Robin thinks he may be up to something. When Robin begins snooping, she discovers that Barney has been taking a class all about Robin that is being taught by Ted. Robin crashes the class and lets Barney know that there is no simple course to learning about her, he must learn from experience.
Marshall and Lily have been yearning for another couple to double-date with despite the number of failed dates they have had with other couples. Thrilled that there is finally another couple in their group, Marshall and Lily invite Barney and Robin over their apartment for game night. When Marshall and Lily are overbearing throughout the double-date, Barney and Robin create some space between the two so that they can avoid another painful evening. Meanwhile, Ted has been testing his luck with the ladies at the bar. Just when Ted thinks he is becoming a ladies’ magnet Barney and Robin alert him to the idea that these women are only flirting with him to have a convenient place to crash after a night at the bar. For this, they deem Ted the “sexless innkeeper.” Marshall and Lily show up to the bar with a brand new couple, one they actually get along with. Barney and Robin realize that they miss their friends and surprisingly have a longing for double-dates as well.
When Marshall and Ted hear about the closing of one of their favorite road trip destinations, they decide to re-live their bachelor days and drive to Chicago. To the behest of Ted, Marshall decides to bring Lily along and she completely alters Ted's plan for a macho weekend. Robin's pride for Canada lands her in troubles when she breaks an American's nose and faces deportation. In order to become an American citizen, Robin starts preparing for the citizenship test with the help of Barney. Lily leads Ted and Marshall to a bed & breakfast catering specifically to couples which makes Ted feel even more isolated and unhappy about the outcome of their road trip. Ted tricks Marshall into leaving the bed & breakfast without Lily so that they could finally attempt to have the trip that Ted had planned. Robin is ready for the citizenship test but after a drunken night Barney must go rescue her from Canada. Robin decides that rather than become a full-fledged American citizen, she will hold on to her love for Canada by applying for dual citizenship. Marshall and Ted reach Chicago but Marshall misses Lily. Ted confronts Marshall about spending time only with Lily and while Marshall is initially offended, the two find a common ground and reunite on the way back to the bed & breakfast.
When Barney witnesses Marshall performing a chore in the house, he thinks Marshall and Lily are headed towards divorce. To save his friend from this fate, Barney offers Marshall relationship advice that Ted strongly thinks should be ignored. At the same time, Robin and Barney are flaunting their happy relationship around the crew –- kissing and using pet names constantly. Ted suspects that something is up with the couple and that they are not as perfect as they seem to be. When Barney’s advice blows up in Marshall’s face, Barney claims even more that he and Robin have the ideal relationship and never fight. However, Ted soon reveals that Robin and Barney have been arguing non-stop when alone. Robin and Barney fess-up to their less-than-perfect relationship and seek advice from Lily and Marshall.
Barney and Robin begin to let themselves go as they get into a relationship rut. When Barney donates his porn collection to Ted, sending a message to Ted, Lilly and Marshall that he's not the same person anymore, the group conspires to break Barney and Robin up. Ted, Lilly and Marshall set up a stake out in a station wagon following the pair. They try to break them up by forcing the issue of commitment and having an engagement ring appear in a glass while Robin and Barney are having dinner but inadvertently cause the two to apathetically agree to marriage. In another attempt, Ted, Lilly and Marshall realize their orchestrated attempts using Robin and Barney's top five fights of all time are unnecessary and they let the relationship take its course. Robin and Barney realize they miss being who they were before they became a couple and break up.
Following his breakup with Robin, Barney intends to revert right back to his old ways: tomcatting around, and lying to women to get in their pants. Lily is opposed to it, and goes to great lengths to stop it –- by stealing his playbook. It’s an episode that explores the question: After a breakup, is it possible to return to being the person you were before the relationship began?
When Lily’s estranged father shows up unannounced on Thanksgiving, we learn what led her to stop speaking to him three years ago. Marshall and Lily fight over their differences in philosophy -- Marshall believes one should maintain connections to their family no matter what, while Lily believes she’s eliminated a truly negative element from her life. Lily ultimately gives her dad a second chance when she realizes what could happen if she waits until it’s too late.
The gang tries to help Ted when the perfect girl is finally available, and Marshall takes action when he finds a letter written by his younger self.
Robin is excited when she’s assigned a new co-anchor at work, the hard-hitting and legendary newsman, Don Frank. Robin quickly realizes Don Frank is not the consummate professional she thought he was. Instead, he’s a washed up, bitter man who seems perfectly happy to take Robin’s professionalism and career down with his. Meanwhile, Marshall, driven by his own stress at work, gives into an old vice by bumming a cigarette from Robin. In a domino effect, the entire group (who we learn are all former smokers) gets re-addicted, and must try to quit all over again.
While Barney must choose between bedding the bar's hot bartender or his beloved suits, Ted gets one step closer to meeting his future wife.
When Lily finds out the co-worker Marshall is always telling funny stories about is actually a woman, she doesn't get as jealous as Marshall would have hoped. It is not until Jenkins kisses Marshall that Lily finally gets mad. When Robin finds out Ted's students watch her show, she gets a little full of herself until she realizes that her show is the basis of a college drinking game.
With Barney approaching a personal milestone, "the Perfect Week," which is to sleep with the first girl he hits on seven nights in a row; and he relives this all through an imaginary interview with Jim Nantz. The gang rallies around him in support. However, it soon becomes clear he's using this personal goal as a diversion from a much larger problem which is that he may get fired at work. Meanwhile the gang uses Barney's situation as their own diversion -- Ted has insulted one of his students, Lily and Marshall shock a couple by revealing they share a toothbrush and Robin waits desperately for a call from a date earlier that week.
Barney holds up a sign with his phone number during the Super Bowl and is besieged with responses from women. He cannot help himself from taking every call and trying to trump the girl he is with. It is one week until Valentine’s Day and Ted has decided to let Marshall and Lily arrange a blind date with someone, claiming he will marry them. Don invites Robin to his house under the guise of a party, however, when she arrives with Ted, they find Don alone and naked in the living room and they uncomfortably leave. Although content with Robin now eating pizza and watching the “Puppy Bowl”, he has to go meet the “arranged” date; Marshall and Lily use one of Barney’s many discarded girls, as they forgot they were supposed to set him up. Lily ends Barney’s obsession with nonstop girls calling and looking to trump each one by dropping his phone in a pitcher of beer. In the end, Ted and Robin are together on Valentine’s Day watching the “Puppy Bowl”. The next day, Don apologizes to Robin for his behavior at work (not being naked last night), and proves it by finally wearing pants, and it’s clear she likes him.
As a result of Ted being "hooked" on Tiffany, the gang reflects about relationships where one person is “hooked”; being strung along by another who wants something more. Scooter, the "lunch lady" at Lily's school is hooked on her, and she and Marshall practice letting him off the hook and both have trouble hurting his feelings. Tiffany humiliates Ted by showing up with her boyfriend at a weekend wedding get-away, and neglecting to dis-invited Ted, who has set up a romantic dinner for them in their room. This is a real eye-opener for Ted, and ultimately lets him off the hook.
After Robin interviews Anita, the author of a dating book “Of Course You’re Still Single, Take a Look at Yourself You Dumb Slut,” she arranges for her to seduce Barney to get back at him for his insensitivity to her after their break up. Following her own guidelines Anita will not sleep with Barney until the 17th date. Due to Barney’s frustration Ted constructs a “superdate” guaranteed to melt any girl. Perpetuated by Robin’s anger that Barney never took her on a date like this when they were dating, she admits that his blatant philandering has been painful for her, and she can’t move on with her co-anchor Don as a result. Barney realizes what he is done and to make it up to Robin he promises he will not sleep with Anita, who of course, is all over him now that he is rejecting her. In addition, he turns over his “superdate” plans to Robin who goes with Don and has an amazing time.
It is Lily’s birthday, and she (and Marshall) make a huge deal out of it every year. She is counting on it just being the 5 of them for their dinner celebration, when once again; Ted turns up with a new girlfriend who “could be the one.” Through a series of flashbacks inspired by photos we see all the special occasions Ted has “ruined” by bringing a stranger. However, in the end Lily is much more sympathetic to Ted as we learn he insisted Lily get in Marshall and Ted’s first college roommate photo just a few weeks after they had started dating. In addition, it seems Barney, throughout the years and currently cannot take a bad picture. He looks exactly the same and perfect no matter what. On the other hand, Marshall can not take a good picture, looking awkward in every photo.
Marshall tries to downplay that he got mugged at gun point while crossing through Central Park on his way home from work. Robin gives him a gun so that he will feel safe. Later at the bar, Lily tells the gang she is applying for a gun license because she believes it will make her feel safer. Marshall does not think it’s a good idea. Meanwhile Barney has been promoting the advantages of a good lie, as depicted in various flashbacks. Lily is so worried about Marshall that he tells the gang “what really happened.” He stopped at the Central Park Zoo on the way home to look at the monkeys. He got too close to the cage and the monkey grabbed him by the lapel and took his wallet out of his breast pocket. Robin has been desperate for an interesting interview for the show so she asks Marshall to come on and tell the story of his “monkey mugging”. While doing the interview with Robin he admits during commercial break that he was not mugged by a monkey, but just said so so Lily would not pursue buying a gun. Robin doesn’t care if it is true, she needs him to tell the story as she really needs a good interview; but she can’t go through with it in the end. Robin has to put Ted on the show to talk about his Empire State Building reproduction that he’s been begging her to have him on about. We never find out how Marshall really lost his wallet, but Lily did not get a gun and Robin maintained her journalistic integrity.
Ted’s mother is getting married for the second time. In addition to being extremely disturbed by his mother Virginia and her fiancee Clint’s overt hippyish displays of affection at the wedding, he questions how far behind his own life is. He leaves the gang and the wedding abruptly not being able to stand another second. He goes to see Sonya his “go to” girl while in his hometown to discover that she is married and pregnant. He then finds a real estate auction site on line and buys a dilapidated house, and takes the gang to see it. Despite his friend’s negative reactions to his impulse buy and massive teardown ahead of him, they do realize that sometimes you need to take a leap of faith. Ted goes back to his childhood home and gives his mother and stepfather the heartfelt toast he did not deliver at their wedding. In the end he is talking to his kids in the traditional shot of the study in 2030, and he ends this tale telling them that their house is actually the same house he bought in the story.
When Don asks Robin to move in with him she feels it is time for him to meet Ted and Barney. Marshall and Lily go on a weekend trip to a bed and breakfast and the only room available is the "Fishin’ Buddies" suite which has twin beds. They have a fantastic night’s sleep and decide to get twin beds at home. Lily becomes concerned that they will grow apart when she learns that separate beds caused Don and his now ex-wife to drift apart. Just when she thought Marshall wanted to keep the separate beds she wakes up to him cuddled up in her twin bed. As Don discovers and learns to accept that Robin's best friends are her ex-boyfriends, Barney and Ted each decide they want Robin back now that she is getting serious with Don. However, both realize they are just jealous that she has moved on. Robin decides to move in with Don and take a break from Ted and Barney so she can give this relationship a real chance.
Barney gets tickets for Robots vs. Wrestlers and wants to start a tradition that they whole gang goes every year. Meanwhile, Ted and Marshall have been receiving mail for Marissa Heller, the former occupant of their (now Ted’s) apartment for years, and have created a profile of her based on what she is sent. When Marissa Heller receives an invite to a party for the same night, at a very special architectural building that Ted has always wanted to see the inside of, they all decide to go to the party before the event. However, Robin has plans with Don and cannot join them. At the party, the gang is bored by the intellectual crowd including Peter Bogdonavich and Arianna Huffington however, Ted is so stimulated by all the intellectuals at the party, including the actual Marissa Heller, that he wonders if it is time for him to branch out from the gang like Robin has. The others go on to Robots vs. Wrestlers without him and Lily and Marshall discuss starting a family, and Barney panics that the gang is falling apart. At the end of the event they see Ted’s doppelganger; a Mexican wrestler. In the end both Robin and Ted reconnect with the gang at the bar, embracing all that they are to each other.
Ted realizes that everyone dating in their 30s has some sort of emotional baggage that they carry with them, making ever harder to find “the one.” He takes his date Royce, (who has yet to reveal her baggage) to see a new movie “The Wedding Bride” and is horrified to discover that it is written by Tony, the man Stella left him at the altar for, and the story is all about his experience of being left at the altar by Stella for Tony. In the movie, Ted is portrayed as a total jerk, Stella is the victim and Tony her savior. Ted’s being left at the altar is his baggage he realizes, and admits the truth to Royce after freaking out about the movie. In the end she gives Ted another chance only for him to discover her baggage; that she sleeps in the same bed as her brother.
Marshall and Lily put fate to the test when deciding whether or not they are ready to have a baby.