The Big Bang Theory Season 12, Episode 12 : The Propagation Proposition

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. Guest Stars: Brian George, Brian Thomas Smith, Rati Gupta, Shay Ali, Chip Chinery, Lindsey Kraft,

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