<P> `` The Recombination Hypothesis '' is the 100th episode of the American sitcom The Big Bang Theory and the 13th episode of the series ' fifth season . It premiered on CBS in the United States on January 19 , 2012 . In this episode , Leonard impulsively asks Penny out for dinner on a date . </P>
<P> `` The Recombination Hypothesis '' is the 100th episode of the American sitcom The Big Bang Theory and the 13th episode of the series ' fifth season . It premiered on CBS in the United States on January 19 , 2012 . In this episode , Leonard impulsively asks Penny out for dinner on a date . </P>
when do leonard and penny start dating again
when do leonard and penny start dating again
13th episode of the series ' fifth season
13th episode of the series ' fifth season