Sheldon lets Penny wait for the locksmith in his apartment after she accidentally locks herself out.
Penny, frustrated at making no progress in her acting career and not having had sex for six months, becomes curious on seeing Sheldon play Age of Conan.
Soon their relationship progresses into a stronger friendship than before, while Sheldon and Penny's friendship slowly begins.
In the season finale Penny hints at her true feelings for Leonard.
Barry Kripke played by John Ross Bowie makes his first appearance In the series starting with this season, He first appears in "The Killer Robot Instability".
Following the Season 1 finale, Leonard and Penny return from their first date while Howard and Raj spy on them using a webcam in the hall between their apartments.
He helps Penny get started; she buys the game and soon succumbs to video game addiction, annoying Sheldon by persistently asking him for game tips night and day.
In desperation he asks Leonard for help, who tries to talk with her in her apartment, but she practically ignores him.
Sheldon attempts to fix Penny a date with the aid of an online dating service, but fails.
In the end, Penny is horrified to realize she has accepted a virtual date with Howard, and promptly stops playing, thus overcoming her addiction.
During their dates, Leslie asks how many children they should have and evaluates Leonard's genetic defects.