Leonard and Penny are no longer dating. Leslie Winkle, played by Sarah Gilbert, moves in on Leonard and proposes to revisit their relationship. Leonard kicks Sheldon out of their apartment so he and Leslie can be on their date alone. Sheldon, who hates Leslie, continually interrupts their date. Sheldon asks Penny for advice on how to break up Leonard and Leslie. He even suggests that Penny get back together with Leonard. Penny comes back with her date and sees Leonard and Leslie. Both Penny and Leonard try to make each other jealous by making out with their respective partners. In the end, Leslie breaks up with Leonard because he supports Sheldon's String Theory over Leslie's Loop Quantum Gravity.
