Episode Guide :: Season 2
The Big Bang Theory's second season mainly focuses on character development and has few overarching plotlines. Leonard and Penny's relationship, which started with a date in the first season finale, ends quickly when Penny worrys she's not smart enough for Leonard. When Leonard suggests she go to college, she slams the door in his face. Leonard and Penny quickly patch up their friendship. Penny's feelings for Leonard become clearer at the end of the season, as Leonard and the guys heads away for a three-month expedition in the Arctic.
Sheldon grows more comfortable with Penny being a part of their social group during the season. A key moment in their friendship comes when Penny gave Sheldon a napkin signed by Leonard Nimoy for Christmas. Howard's womanizing ways continue throughout the season, though the break-up of his short-term relationship with Leslie Winkle reveal his more sensitive side. Raj has a moment of success when he discovers a trans-neptuinian planetoid and later shows signs of progress when he's able to briefly apologize to Penny without drinking any alcohol.
The Big Bang Theory's second season contained twenty-three episodes aired between September 22, 2008 and May 11, 2009. The show was renewed for a further two seasons in March 2009. The Big Bang Theory ranked #44 in the ratings at the end of its second season.