[s4e20] The Herb Garden Germination Here

: 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).

: Renowned physicist Brian Greene appears as himself, giving a book reading that Sheldon and Amy attend specifically to heckle. [S4E20] The Herb Garden Germination

: Refers to the mundane "control" rumor Sheldon and Amy used for their social experiment. : After hearing a rumor from Penny that

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 : Refers to the mundane "control" rumor Sheldon

: 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.