In the fourth-season opener, Stella gives Ted an answer to his proposal, and Barney realizes he's in love with Robin. Stella: Sarah Chalke. Mark Johnson: Kyles Archer. Sexy Blonde: Nicole Taylor. Angela: Dana de Celis. Maxine: Annie Abrams.
Marshall runs into Regis Philbin during his search for the restaurant where he ate his first New York burger.
Ted invites his friends to Stella's New Jersey apartment, and he tries to convince them that living outside the city has benefits---until Stella says she wants to live there permanently after they're married.
Ted learns his friends ditched plans for an intervention for his engagement to Stella, but he insists they go through with it anyway.
Ted and Stella decide to get married in three days, but the reappearance of their exes puts a damper on the occasion. Lucy: Darcy Rose Byrnes. Tony: Jason Jones.
While out with his friends, Ted bumps into a past acquaintance whom he'd rather avoid, prompting everyone to discuss how they would react in the same situation. Eric Braeden guest stars.
Lily and Marshall contemplate having a baby, and Lily asks Robin and Ted for advice.
Robin reunites with a group of party-hearty single girlfriends known as the "Woo Girls." Meanwhile, Ted submits to Barney a design for his company's new headquarters. Jamie-Lynn Sigler guest stars.
Ted encounters one of Robin's dates sitting naked on her couch, and the guys conclude the unorthodox approach might work for them as well.
Ted and Barney pick a fight with guys sitting in their favorite booth in an attempt to change how their friends perceive them. Doug: Will Sasso.
Ted's younger sister visits, and he does everything in his power to keep her away from Barney. Meanwhile, Marshall takes Robin to a Minnesota-themed bar.
Robin and Ted become "friends with benefits," finding it helps them get along better in the apartment; reality stars Heidi Montag, Spencer Pratt, Kendra Wilkinson and Kim Kardashian taunt Marshall from the pages of magazines.
A blizzard hits the city as Lily is returning from a trip to Seattle, threatening an airport-reunion ritual between her and Marshall. Meanwhile, Ted and Barney plan to meet two women at MacLaren's, but Carl wants to close early, so the guys volunteer to watch the bar until their dates arrive.
Robin has only four days to find a job or she'll be deported, and Barney steps in to help by producing her video résumé.
When Barney inexplicably leaves MacLaren's, the gang thinks he has a girlfriend. Loretta: Frances Conroy. Margaret: Brooke D'Orsay.
Ted reunites with his college girlfriend (Laura Prepon), prompting Lily and Marshall to reveal how much they loathed the snooty woman.
When Ted's girlfriend, Karen (Laura Prepon), finds a woman's earring in his bed, Ted learns that Lily put it there. Worse, it turns out she's been sabotaging his relationships for years.
Barney and Marshall dream up an intricate lie to protect Ted from finding out he's lost an important job.
Ted's list of "things the gang's too old to do" prompts Barney to attempt everything on the list within 24 hours just to prove Ted wrong.
Ted sets up his architecture firm in his apartment and hires an intern, who ends up getting a little too chummy with Ted's friends.
Ted starts texting a woman (Rebecca Budig) he recently met, breaking one of Barney and Marshall's relationship rules, so the pair pretend to be the woman to play a joke on Ted.
Ted runs into an old flame and learns a life lesson about destiny. Meanwhile, Barney celebrates his 200th. No need to explain more. Milt: Dan Castellaneta.
An acquaintance of Ted's feels guilty about a previous wrong and tries to atone for it by helping Ted get a job. Meanwhile, Barney thinks he can talk his way out of a speeding ticket.
In the fourth-season finale, Ted works feverishly to promote his business while Marshall tries to get him to the roof for a surprise 31st birthday party.