[s4e20] The Herb Garden Germination -

: Renowned physicist Brian Greene appears as himself, giving a book reading that Sheldon and Amy attend specifically to heckle.

: The episode concludes with Amy starting an even more extreme rumor—telling Penny she is pregnant with Sheldon's baby—to see how quickly Leonard finds out. Original Air Date April 7, 2011 Director Mark Cendrowski Major Milestone Howard and Bernadette get engaged

: Unaware of the breakup rumors, Howard plans to propose to Bernadette. While the rest of the gang expects a public rejection based on the gossip, Bernadette surprises everyone by accepting his proposal. [S4E20] The Herb Garden Germination

: As expected, the "juicy" rumor spreads like wildfire through the group, while the herb garden news is completely ignored.

: The engagement is particularly devastating for Raj, who had been harboring a secret crush on Bernadette and was hoping the breakup rumor was true. Key Episode Details : Renowned physicist Brian Greene appears as himself,

: Refers to the mundane "control" rumor Sheldon and Amy used for their social experiment.

: After hearing a rumor from Penny that Bernadette is considering breaking up with Howard, Sheldon and Amy decide to study "memetic epidemiology". They intentionally plant two rumors to see which spreads faster: a salacious one (that they had sex) and a mundane one (that they are starting a herb garden). While the rest of the gang expects a

In the The Big Bang Theory episode (Season 4, Episode 20), the plot centers on a social experiment conducted by Sheldon and Amy to test the speed and "virulence" of gossip within their friend group. Plot Summary