The fourth season of the American television comedy series How I Met Your Mother premiered on September 22, 2008 and concluded on May 18, 2009. It consisted of 24 episodes, each running approximately 22 minutes in length. CBS broadcast the fourth season on Monday nights at 8:30 pm in the United States. The complete fourth season was released on Region 1 DVD on September 29, 2009. In the United Kingdom it began airing via E4 from Thursday, December 10 weekly.
To date, it is the only season of the series to be nominated for the Primetime Emmy Award for Outstanding Comedy Series.
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.
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.
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.
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.
Ted and Stella move up their wedding date, but the wedding may not go off as planned after Ted breaks the "No Exes Rule" and invites Robin to come in from Japan for the wedding.
A serendipitous meeting with someone from his past has Ted thinking about how he would handle running into someone he would prefer to forget.
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.
A birthday party for one of Lily's co-workers leads to Robin connecting with a group of single partiers known as the "Woo Girls". Ted presents a plan for Goliath National Bank's new HQ.
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.
Ted (to prove he's not a milquetoast) and Barney (to impress Robin) pick a fight with a group of guys sitting in the gang's favorite booth at MacLaren's.
Ted tries to keep his irresponsible sister from hooking up with Barney during her trip to New York, and Robin starts hanging out with Marshall at a bar for Minnesotans, not telling them that she's really Canadian.
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.
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.
Robin, desperate to find a job before she is deported, agrees to let Barney produce a video resume for her.
The gang thinks that Barney must have a secret girlfriend after noticing his bizarre behavior.
Marshall and Lily are less than thrilled when they hear that Ted's college girlfriend (Laura Prepon) has moved to New York.
Ted learns that not only did Lily plant another woman's earring in his bed for Karen to find, she has meddled in some of his other relationships as well.
Marshall and Barney lie to keep Ted from finding out the headquarters he'd been hired to design for GNB has been cancelled.
When Barney learns Ted has a list of things he thinks the gang is too old to do, he sets out to do every task within 24 hours in order to prove Ted wrong.
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.
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.
Ted ponders how being in the right place at the right time can impact a person's life; Barney celebrates his 200th female conquest.
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.