When aliens mistake broadcasts of classic arcade games as a declaration of war and attack using tactics from the games, a 1980s video game champ is called upon.
Sheldon goes behind Mary's back to explore Germany on his own; Missy tries to pull one over on George Sr.; Meemaw and Dale work out their new arrangements.
After having a fight with Chandler, Joey decides to move out; Rachel and Phoebe decide to get tattoos; Monica's father disapproves of her dating Richard.
Phoebe is discovered by a record producer who wants to make "Smelly Cat" a video; Joey considers moving back in with Chandler, but Chandler has a new roommate.
Creeped out by his bizarre new roommate, Chandler demands he move out; a new book on female empowerment inspires the ladies to have a "goddess meeting."
Phoebe's world view is shattered when she learns how "Old Yeller" really ends; Monica becomes jealous when Richard begins going out with Joey and Chandler.
Chandler and Ross run into two bullies at the coffee shop; Monica is forced to get a job at a 50's theme restaurant after losing her cash in the stock market.
Phoebe catches chicken pox just as her old flame arrives in town on leave from the Navy; Joey gets a job at Chandler's office but decides to play it as a role.
When Sheldon's twin sister Missy visits, Leonard, Wolowitz and Koothrappali become infatuated with her, and Leonard comes up with plan to eliminate the others.
Penny tries to plan a surprise birthday party for a reluctant Leonard, but she gets sidetracked when Sheldon tries to live his fantasy in an electronics store.
Sheldon introduces Penny to the world of online video gaming, but he soon realizes his mistake when she gets addicted and constantly pesters him for advice.
Penny vows revenge on Sheldon after he bans her from the apartment for a series of petty infractions; Howard and Raj look for "The Next Top Model" house.
When Leonard's new relationship starts moving too fast and he finds himself unable to say "no," he turns to Penny for advice; Sheldon tries to cure his ears.
Christmas becomes a stressful time for everyone as Leonard's handsome colleague starts dating Penny and Sheldon pesters the gang with his gift etiquette.
Ten teams enter the qualifier, while six teams will move on to the grueling gauntlet, and the two teams to finish first will then enter the Wipeout course.
Stan's ideal Thanksgiving plans of celebrating in his underwear while watching football are hindered when Francine invites her adoptive guardians over.
Snot gives a lesson to Roger about the nuances of the practice of Hanukkah, but this has unintended consequences when the lesson is taken too seriously.
When Stan takes over Bullock's class at the CIA Academy, he shares his uneventful stories with the cadets; Klaus becomes the hype man for a renowned rapper.
Stan is persuaded to run for mayor to fund construction for a bullet train that would ease morning traffic, but his mayoral duties cause him a lot of stress.
After becoming the new guidance counselor at her kid's school, Francine begins hanging out with a group of tough women; Jeff becomes upset over his lost hat.
After realizing they're interested in the same guy, Maxine and Laura jeopardize their friendship and get into a competition; Carl questions Mother Winslow.
Steve Urkel uses his time machine to travel into the 1970s with Carl, who uses this as an opportunity to change the future and make himself a billionaire.