The Big Bang Theory
The Propagation Proposition
Season 12, Episode 12 · Aired 2019-01-10

Synopsis
Penny's ex-boyfriend, Zack, and his wife want a baby, but when Zack is infertile, they ask Leonard for help. Also, Koothrappali attempts to mend things with his ex-fiancée, Anu.
In the series
This episode is part of The Big Bang Theory (2007–2019) on CBS.
Nerd culture goes multi-cam prime-time global.
Key cast
- Johnny Galecki as Leonard Hofstadter
- Jim Parsons as Sheldon Cooper
- Kaley Cuoco as Penny
- Simon Helberg as Howard Wolowitz
- Kunal Nayyar as Raj Koothrappali
- Mayim Bialik as Amy Farrah Fowler