So season 3 has started airing in some countries (not this one, damn)

Season 3: Episode 1: The Electric Can Opener Fluctuation

After their return home from their three-month expedition in the North Pole, Sheldon finds out from Howard and Raj that the guys had tampered with his experiment because Sheldon was absolutely unbearable when he wasn't getting the results he wanted. They tell him about their use of an electric can opener to give Sheldon positive results, thereby causing Sheldon to believe he has made a Nobel Prize-winning discovery. Unfortunately, Sheldon had immediately emailed everyone at Caltech about his discovery before Howard and Raj could tell him what had happened. Sheldon is so disgraced that he resigns and moves back in with his mother (played by Laurie Metcalf), who lives in east Texas. Mrs. Cooper calls Leonard and tells them that they should come talk to Sheldon. Upon the guys' arrival, Sheldon is intent on staying in Texas. However, he shortly has a disagreement with his mother about creationism versus evolution and decides to return home.

Meanwhile, Penny has been harboring feelings for Leonard, which are released almost as soon as he comes home. Leonard's "moments" with her are constantly interrupted, and he "cannot catch a break." They finally sleep together at the end of the episode (Leonard finally "catches his break") and Leonard asks why it's always weird after friends sleep together and why they have to label it as such - "it just is what it is." Penny interrupts him saying "it's weird" and he replies "Totally."

Season 3: Episode 2: The Jiminy Conjecture

Leonard and Penny struggle to recover from an awkward first hookup and try to figure how to overcome their current problem. A romantic evening between the pair soon turns to a night filled with drunken sickness. The next day Penny talks to Sheldon regarding her current problem with Leonard and Sheldon points out that if things don't work out, they can always return back to being friends. After Sheldon tells Leonard that he spoke to Penny about their problems, Leonard goes to Penny's apartment, there Penny tells Leonard that being friends was much simpler and that it will take the pressure off, something that Leonard agrees to. They decide to go back to being friends, however it's clear that neither wants that and soon they are pretty much back on. Meanwhile, Sheldon and Howard stake their most valuable comic books (Sheldon's Flash against Howard's Fantastic Four) on a bet to determine the species of a cricket. Sheldon hears the chirps and says it is a snowy tree cricket and Howard insists it is a common field cricket. Along with Raj, the three spend a while locating the cricket. They settle the bet by taking "Toby" to Caltech's depressed entomologist, played by Lewis Black.