Penny's claim that Leonard has stopped trying in their marriage is somewhat unreasonable, since Leonard has always been the one to put most of the effort in their relationship. This previously led to a clash in The Tangible Affection Proof (2013) after Penny ruined one of Leonard's Valentine's Day efforts, and in The Romance Resonance (2013), Penny agreed to organize a romantic evening because Leonard had done all the previous ones.
Leonard mentions the wine tasting in Santa Barbara where Penny tasted the best rosé she'd ever had. This tasting took place in The Fermentation Bifurcation (2016).
Leonard quotes some lyrics from "(God Must Have Spent) A Little More Time On You" by *NSYNC, which was identified as Penny's favorite boyband in The Platonic Permutation (2015).
Howard claims that he never had sex in his old room, but he did: with Leslie Winkle in The Cushion Saturation (2009), and with Bernadette (implied at least) in The Pulled Groin Extrapolation (2011). In The Russian Rocket Reaction (2011), Bernadette even tried to initiate sex but Howard wasn't in the mood.
This episode was taped on December 13, 2016.