In the third-season finale, "The Lunar Excitation", after Penny's failed attempts to move on from her relationship with Leonard, she becomes intoxicated and has sex with him. In the morning, Leonard believes that their relationship has resumed, though Penny tells him that the previous night was a mistake. This causes a strain on their friendship; at the end of the episode, Leonard becomes intoxicated and tries to have intercourse with her, prompting Penny to push him out of her apartment, to which Leonard suspects a double standard. He immediately makes the same advances towards Leslie Winkle, who replies, 'Let me think about it" and slams the door in his face.