In which episode of the Big Bang Theory does Penny date that other smart guy?

By "that other smart guy" I mean some visitor to their university. He was super smart and had won like a nobel prize or something, but he was actually cool and good looking and wore a leather jacket and had a motorbike. Penny went gaga over him, and Leonard got mad because she was dating him even though she had said she didn't want to date Leonard because he was "too smart for her". The guy wound up being married, so Penny got her heart broken and Leonard wound up comforting her. I'm looking for the title and season of the episode. 10 points best answer!!