The Big Bang Theory Season 9 Episode 22

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.

Episode Title: The Fermentation Bifurcation

Air Date: 2016 04 28