When Sheldon learns the guys tampered with his expedition data he got from the arctic, he leaves to Texas in disgrace. This results in the guys following him, which threatens Leonard's hope for some romantic time with Penny and the guys' friendship with Sheldon.
Sheldon and Howard wager comic books over a cricket's species. Meanwhile, a less-than-perfect romantic night agonizes Leonard and Penny.
Howard takes Raj along to check out the Goth dating scene. Sheldon uses chocolate as part of a behavior modification experiment on Penny.
Facing a return to India, Raj needs a job desperately enough to consider working for Sheldon. Meanwhile, Howard becomes a third wheel to Leonard and Penny.
After overhearing that Wil Wheaton is always entering a trading-card competition, Sheldon decides to enter it himself. Meanwhile, Penny sets up one of her friends on a date with Wolowitz.
Sheldon becomes Leonard's teacher in order to understand football, while an incident with flying a kite threatens Howard and Raj's friendship.
After a fight between Leonard and Penny has some influence on his life, Sheldon is forced to play peacemaker in order to get the couple back together.
Penny is injured, but unfortunately Leonard, Howard and Raj are all away on a camping trip to the desert, so all she has to rely on is Sheldon.
Howard is unsure what to do with his new girlfriend Bernadette, so he discusses it with the guys. However, talking with his friends only makes him take wrong turns.
Penny gets help from Sheldon in order to understand what Leonard's work is, while Wolowitz develops a jealousy when Leonard starts hanging out with his new girlfriend.
Leonard fears the worst for his relationship with Penny when his mother visits, while Sheldon is nothing but thrilled with Beverly's presence.
Leonard becomes upset when he discovers the fact that Penny believes in psychics, while Sheldon and Koothrappali attend a university mixer together.
After their apartment is robbed, Leonard and Sheldon get Raj and Howard to help them create a state-of-the-art security system.
Sheldon's search for the answer to a physics problem leads him to work at the Cheesecake Factory with Penny.
Leonard can only bring one guest on a trip to see CERN's Large Hadron Collider (the world's largest and highest energy particle accelerator) in Switzerland on Valentine's Day.
Sheldon winds up in traffic court when he gets a ticket because of Penny.
When the guys find a ring from "The Lord of the Rings" at a garage sale, it threatens to tear them apart.
Sheldon's friends come to his aid when his fear of public speaking stands between him and a coveted award.
Leonard and Penny's relationship is on the line when they start fighting.
When a fight leads to Penny and Leonard no longer speaking to each other, Sheldon goes to extraordinary lengths to try to keep them both happy.
Leonard and Sheldon vie to catch the eye of a visiting female physicist.
Leonard recounts for Penny the story of how he met and moved in with Sheldon.
Howard and Raj try to find the perfect match for Sheldon by setting him up on an Internet dating site. Penny is worried that after dating Leonard she won't be able to date normal guys.