As Howard awaits blast-off, he recounts how the gang threw together a last-minute wedding for him and Bernadette.
A bachelor party and his sexual past puts Howard's marriage to Bernadette in jeopardy.
When Stephen Hawking visits Caltech to give a lecture, Sheldon goes to great lengths for a chance to meet his hero in person.
Sheldon faces a crisis of conscience after breaking a Star Trek toy given to him by Penny. Meanwhile, a lonesome Raj is smitten after a date set up by his parents.
Sheldon incurs Amy's ire when he chooses a weekend of videogaming with the guys over a birthday party for her aunt.
Sheldon is forced into altering his precious schedule after his barber falls ill. Meanwhile, the training required to be an astronaut has Wolowitz wondering if he has the right stuff.
When a new office space is made available, Sheldon goes head to head with his nemesis, Kripke, for the right to move in. Meanwhile, Penny is unsettled by painting given to her by Amy.
Forced to use his vacation time, Sheldon dabbles in biology in Amy's lab. Bernadette reveals to the girls that her father wants her to make Howard sign a pre-nup.
Leonard can't take Sheldon's continued selfishness and agrees to dissolve the Roommate Agreement. Howard wants to have a cool nickname for when he's an astronaut.
Leonard and Penny create lists of 'bugs' in their relationship in an attempt to strengthen it. Meanwhile, Sheldon and Amy create a YouTube video series called Fun with Flags, and Raj develops an unhealthy attachment to Siri on his iPhone.
Leonard asks Penny out on an impromptu romantic date.
Sheldon finds himself in hot water when he doesn't appreciate Amy's recent accomplishment. Howard discovers Bernadette doesn't interact well with children.
Leonard is hesitant when a bully from high school wants to meet for a drink. Meanwhile, Penny comes to realize she was a bully herself.
Sheldon finds himself jealous when Amy goes on a date with Stuart. The other guys can't resist the allure of the latest collectable card game expansion pack.
When it is revealed that Penny and Bernadette went wedding dress shopping without her, Amy becomes heartbroken and pressures Sheldon for sex.
Leonard finds himself drawn towards a comely comic book illustrator. Meanwhile, Sheldon tries to scare the gang for Halloween.
When his mother comes for another visit, Sheldon is disappointed that she's stopped being the mother he wants her to be.
Sheldon is miffed that Leonard plans to attend a party hosted by his nemesis, Wil Wheaton. Meanwhile, Howard is offered a chance to be a payload specialist on the International Space Station.
Penny finds the perfect girl for Raj to date. Meanwhile, Sheldon uses Dungeons & Dragons dice to make life's trivial decisions.
Sheldon is aghast to learn the new chair in Penny's apartment was someone else's garbage. Leonard and Priya try a long-distance relationship.
After spending the night with Raj, Penny is worried that her friendship with the guys is in jeopardy, while Sheldon becomes the paintball team leader.