Amy and Howard begin collaborating on a neuroprosthetics project, upsetting Sheldon and Raj, who feel they are not spending as much time with them. When they seek solace with an annoyed Bernadette, she exploits the situation to trick Sheldon into doing Howard's chores. Penny successfully employs the approaches recommended in one of Bernadette's parenting books to deal with Sheldon, but Leonard believes she is coddling Sheldon too much. Sheldon and Raj resolve the issue of missing their significant others by spending time together.
Campbell and Pemberton start a publicity tour for their Nobel campaign, including appearing on The Ellen DeGeneres Show. Caltech reaches out to previous winners, including George Smoot, Kip Thorne and Frances H. Arnold, only to find that Sheldon has offended most of them in the past. Leonard and Penny convince them to show up to the reception, only for Pemberton and Campbell to crash the party. Leonard holds Sheldon back, only for Amy to verbally snap at them. Meanwhile, with Halley scared of the dark, Stuart and Bernadette turn Howard's story from his time in outer space into the children's book: The Frightened Little Astronaut. Howard is embarrassed until Bernadette talks him into helping children and Stuart's art career by letting it be published.
Johnny Galecki as Leonard Hofstadter: An experimental physicist with an IQ of 173, who received his PhD when he was 24 years old. Leonard is a nerd who loves video games, comic books, and Dungeons & Dragons. Leonard is the straight man of the series, in which he shares an apartment in Pasadena, CA, with Sheldon. Leonard is smitten with his new neighbor Penny when they first meet, and they eventually marry.
Sara Gilbert as Leslie Winkle (recurring season 1, starring season 2, guest seasons 3, 9): A physicist who works in the same lab as Leonard. In appearance, she is essentially Leonard's female counterpart and has conflicting scientific theories with Sheldon. Leslie has casual sex with Leonard and later Howard. Gilbert was promoted to a main cast member during the second season but resumed guest star status because producers could not come up with enough material for the character. Gilbert returned to The Big Bang Theory for its 200th episode.
Well done! Really great final episode writing. The characters we have enjoyed for 12 seasons went on with their lives. . .but reached a happy place at that moment of time. Amy and Sheldon recognized for their brilliance. Penny and Leonard growing into a family. Bernadette and Howard being concerned about the children. Raj having someone fun to attend the ceremony with. Way to tie things up on a pleasant note.
The episode opens with a short montage of clips from the series' twelve seasons, then segues to Sheldon and Amy, who are up late waiting for a call from the Nobel Committee. Following a prank call from Kripke, they are told they've won the Nobel Prize in Physics for their super-asymmetry work. The attention from the media and the university bothers Sheldon. Amy is saddened by an unflattering picture of her in a news report, so Raj convinces her to get a makeover. She loves her new look but Sheldon demands she change it back. Leonard calls him out for being rude, but Sheldon flees when he sees Penny emerge from the newly repaired elevator. Sheldon and Penny go to the Cheesecake Factory and Penny tells Sheldon that change is the only constant thing in life. On a TV, they see Bernadette and Howard take credit as Sheldon and Amy's best friends. Raj and Leonard defend Amy, with Leonard accidentally breaking Sheldon's DNA molecule model in Apartment 4A. Penny convinces Sheldon to ride in the elevator.
^ "Editor's Note: With final Monday ratings in, The Big Bang Theory has now reached a new series high in viewers (16.32m) and was the night's top program in adults 18-49 (5.9/15), up a tenth from this morning. -- "Two and a Half Men" Soars to Its Best Adult 18-49 Rating in Three Years". CBS. March 9, 2010. Archived from the original on January 8, 2014. Retrieved January 5, 2013.