After a shortened season 1 of just 17 episodes we get a full sit-com season of 23 episodes in season 2. After returning from their first date, Penny & Leonard are spied upon by Raj & Howard using a spy camp fixed in the corridor. An awkward situation arises when Leonard finds out that Penny didn’t complete community college and she slams the door in his face when he tries to be supportive. Penny stars seeing Eric upon which Leonard tries to get things started again with Leslie Winkle but she dumps him when he sides with Sheldon on conflicting theories.
Penny is introduced to Age of Conan and gets addicted to it playing it all hours and Raj let’s “fame” go his head when he gets a mention in People magazine for is discovery of the trans-Neptunian object 2008 NQ17, sparking jealousy from his friends. A gradate student becomes obsessed with Sheldon, attaching herself to him as his personal assistant and doing stuff for him. However when Sheldon reaches a breakthrough in his scientific research, she wants to share credit in it and so Sheldon boots her out. We also learn after a fight between Penny & Sheldon that the latter’s “kryptonite” is his mother! Leonard starts dating Dr. Stephanie Barnett, a woman Howard tried to impress, and their relationship becomes serious. Sheldon considersher to be the only “tolerable” girlfriend that Leonard has had. As a result, Sheldon tries helping Leonard in his relationship with Stephanie, as otherwise he thinks Leonard will ruin it. As Sheldon states they now the doctor for their landing party – he says to Leonard “You’re [Leonard is] Kirk, I’m [Sheldon is] Spock, Wolowitz is Scottie, Koothrapalli is the guy that always gets killed…and now we’ve got McCoy [Stephanie]”.
Stephanie and Leonard later break up as he feels that they need to slow down a little. One of the most classic & funniest scenes occurs when Penny gifts Sheldon a napkin both autographed and used by Leonard Nimoy. Sheldon is overwhelmed since he now possesses his DNA and can grow his own Leonard Nimoy and responds by giving Penny many gift baskets and then a rare “Sheldon” hug (“look Leonard Sheldon is hugging me). Penny meets Dr. Underhill, an attractive scientist & visiting researcher through Leonard, and they start dating but she breaks it up when she finds out that he is married. Howard gets depressed when Penny harshly comments about his love life, which results in Howard missing a robot fight competition. We also meet Leonard’s mother, accomplished psychiatrist and neuroscientist Dr. Beverly Hofstadter, who makes her son uncomfortable but seems to get on well with Sheldon. Meanwhile, Leslie and Howard start sleeping together. And ofcourse the four guys meet Summer Glau on a train trip to San Francisco and both Raj & Howard try to hit on her.
The guys help Penny start her own home business, Penny’s Blossom, but they get exhausted as the orders start filling in and it’s only the five of them working on it. Leonard and Raj decide to take him on a trip to Las Vegas, in order to cheer him up after Leslie dumps Leonard while Sheldon, having forgotten his apartment key, is forced to spend the night at Penny’s apartment. Sheldon wins a National Science Foundation grant to go on a three-month expedition to the North Magnetic Pole to detect magnetic monopoles and prove the validity of string theory and takes Leonard, Raj & Howard with him. When Penny learns that Leonard is also going, she is seemingly upset. Later, she gives him a Snuggie as a gift, says she’ll miss him, and gives him an unusually long hug but is unable to tell him that she doesn’t want him to go.