'The Big Bang Theory' - 01/10/2019 (Photo Gallery)

In the episode entitled "The Propagation Proposition," Penny's ex-boyfriend, Zack (Brian Thomas Smith), 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 (Rait Gupta).