The Large Hadron Collision

' The Large Hadron Collision' is the fifteenth episode of the third season of The Big Bang Theory. The episode first aired on February 8, 2010.''

Summary
When Leonard is offered a trip to Switzerland to visit the Large Hadron Collider he plans on taking Penny, however the roommate agreement stipulates that if one roommate goes the other will accompany him.

Extended Plot
Leonard announces that the professor who was invited to a trip to see CERN's Large Hadron Collider in Switzerland was unable to go, so he (Leonard) was designated to be the replacement to go, and he gets to take one guest with him. Sheldon assumes that he would be Leonard's guest because they have a roommate agreement clause that if one roommate gets invited to see the collider, he would invite the other. In spite of the agreement, Leonard chooses to invite Penny, as the trip would coincide with Valentine's Day, their first together as a couple. Sheldon tries to pressure both Leonard and Penny to let him go instead, but Leonard insists on bringing Penny and not Sheldon. The night before their scheduled trip, Penny falls ill, so Sheldon is designated to accompany Leonard; however, Sheldon immediately falls ill too, which he suspects he caught when he hugged Penny the day before when she said that he could go with Leonard. Raj therefore accompanies Leonard, and they arrive in Switzerland to a hotel room stocked with champagne, roses, and chocolates.

Critics
"Sheldon has his moments including a witty retort to Penny calling him an alien: “Extraordinary intelligence might well appear extra-terrestrial to you..."The conclusion of the plot had a kind of justice to it with Raj getting a good Valentine's Day for once and Sheldon not being rewarded for his bad behaviour...The plot could have focused on Penny and Leonard’s relationship and how they were going to cope on their first holiday together. But no, instead we got Sheldon trying to enforce rules, to butter Leonard up and then to convince Penny not to go...Sheldon is unlikeable all the time but he is funny. Leonard comes across as an irritable coward most of the time which isn’t likable. I believe the whole show would benefit from addressing these character flaws. Otherwise we will get more episodes like this where there is no one to like." - The TV Critic's Review

Quotes
Sheldon: Alright, this game is called Traitors. I will name three historical figures and you will name them in order of the heinousness of their betrayal.  Benedict Arnold,  Judas,  Dr. Leonard Hofstadter.

Trivia

 * Sheldon believes Leonard belongs with Judas for the heinousness of his betrayal, an allusion to Sheldon's religious upbringing. On the other hand, Sheldon says Judas had the decency to hang himself after what he did. As Judas was paid with 30 pieces of silver, Sheldon slaps down a tray with 30 pieces of silverware in front of Leonard.
 * Leonard mentions "one giant marble horse," in reference to Howard and Bernadette going to P. F. Chang's China Bistro.
 * Sheldon engages in one of his rare hugs. He later blames his illness on the physical contact associated with the hug.
 * In the commitments under the Roommate Agreement, Leonard can't kill Sheldon if he turns into a zombie, but there is a reciprocity clause; that is, he gets to pull the plug on him, as revealed "The Roommate Transmogrification".