The Big Bang Theory
The Fermentation Bifurcation
Season 9, Episode 22 · Aired 2016-04-28

Synopsis
The gang goes to a wine bar and runs into Penny's old boyfriend, Zack. Also, Bernadette gets stuck spending the evening with Sheldon when she can't go wine tasting with the group, and things don't go as planned when Koothrappali introduces his new girlfriend, Claire.
In the series
This episode is part of The Big Bang Theory (2007–2019) on CBS.
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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