The bar where Zack buys Penny's Posse a bottle of champagne is the same bar from The Alien Parasite Hypothesis (2010) where Amy had her first spontaneous sexual arousal (which also involved Zack).
Near the end of the episode, when Penny is telling Leonard that she supports his decision, the front of the refrigerator is clearly visible behind Penny. Attached to the freezer door are two pictures of Leonard and Penny. One is of them in her apartment on her couch. The other appears to be a still image from The Nerdvana Annihilation (2008). It shows Leonard, without his glasses, holding Penny in the elevator shaft. Other items on the refrigerator include a periodic table, the apartment's official flag, post-it notes, a notepad, and multiple take-out menus.
First appearance of Lindsey Kraft as Zack's wife Marissa. In The Cognition Regeneration (2017), Zack was engaged to a woman called Sarah, indicating that this relationship has since ended.
