Two friends aspiring to be club promoters get fired from their house cleaning jobs and they decide to throw a massive bash at their latest cleaning site.
Steve confronts Laura when he discovers that Ted has bragged to his friends that he and Laura have become intimate; Laura attempts to curb a rumor about her.
Sheldon is a less-than-stellar patient when he is forced to spend multiple days in the hospital; Missy learns what life could be like without her twin.
Sheldon and Dr. Sturgis get into their first fight when one of Sheldon's test answers is marked wrong; Mary assumes the responsibilities of Pastor Jeff.
Sheldon causes chaos when he decides to boycott his favorite company that makes bread; Georgie offers to console Veronica after her boyfriend dumps her.
The gang learns that Rachel is pregnant; Joey tries to impress a Broadway director who's dating Chandler's mom; Chandler's shoes make it hard for him to dance.
Joey finds a sweater from a one-night stand that Rachel had a month ago and deduces that it belongs to the father; Joey proposes to both Phoebe and Rachel.
Ross and Rachel argue over who initiated their latest tryst, so they go to Ross's video to prove who came on to who; Monica and Chandler talk about honeymoon.
Joey sets Rachel up on a date with one of his co-stars, which doesn't sit well with Ross; Ross discovers that a coworker of Chandler's has been calling him Toby
Amy discovers that Sheldon has requested a one-way trip to colonize Mars; Leonard surprises Penny with an "adult" item; Raj prowls around Emily's apartment.
An article about Sheldon and Leonard's joint research paper fails to recognize Leonard; a power outage at Mrs. Wolowitz's house results in a final dinner.
Sheldon and Amy construct a fort and have their first sleepover; meanwhile, Howard receives a visit from an unexpected guest who claims to be his half-brother.
Raj must deliver a message on behalf of NASA that will announce the potential future discovery of alien life forms; Penny considers returning to acting.
Leonard gives a speech to the students graduating from his old high school; Wolowitz doubts his abilities when he and Sheldon fail to fly a remote helicopter.
As Sheldon and Leonard prepare to accept an award for their paper, they receive a visit from both their mothers; Bernadette wants help keeping the house clean.
Amy takes some time away from Sheldon to collect her thoughts; Leonard and Penny's wedding plans are uncertain as Penny comes to terms with his infidelity.
Sheldon is interviewed for a film concerning Spock from "Star Trek"; Wolowitz disagrees with Bernadette over making renovations to the home he grew up in.
Phil builds a habitat for the duck eggs and convinces Lily to help him hatch them; Claire is anxious about telling Jay and his team about her ideas for closets.
Claire wants to make sure that Haley and Alex have fun on "Bring Your Daughter to Work Day"; Phil helps Luke and Manny's class with community service day.
While eating Thanksgiving leftovers at Jay and Gloria's house, everyone decides on their own to sneak into the house that Phil is selling; surprise family trip.
Gloria wins a family seminar with the author of "Clean Out Your Junk Drawer," Debra Radcliffe, who encourages people to get rid of their emotional junk.
Claire and the children are of tired the ducks being in the house, so they try to get rid of them while Phil is visiting Alex at college; Lily has a sleepover.
The Ghost of Christmas Past tries to revive Stan's holiday spririts, but he seizes the opportunity as a chance to change the outcome of the Vietnam War.