In this episode, Penny is back in her old apartment where Sheldon and Amy are now living. She is trying to point out on behalf of Amy that Ramona has an interest in Sheldon. When Sheldon gets up to go update his resume, Penny turns and looks at the hideous painting of her and Amy. This painting was given back to Leonard and Penny in the episode The Property Division Collision (2016), and they hung on their wall because they couldn't find a reason for Amy to keep it herself. Apparently, they eventually found a way to give it back to Amy.
Amy's hotel room is her former apartment
Sheldon apparently angered Patrick Stewart, making him the third Star Trek actor with whom he is no longer welcome. The other two are Leonard Nimoy, who had a restraining order filed against him, and LeVar Burton, whose contact details he had to destroy.
After all this time, Leonard has finally discovered that Lactaid tablets can help his lactose intolerance.
Ramona Nowitzki (Riki Lindhome) makes a return after her previous appearance in The Cooper-Nowitzki Theorem (2008), 208 episodes ago.