Sheldon wonders if he should start watching The Flash. On that show, one of the characters, Cisco, is seen wearing a Bazinga t-shirt in at least one episode.
There is a framed photo of the late Carol Ann Susi in Howard and Bernadette's house (on the shelf just above their dolls).
This is the second time one of the guys has wondered about the possibility of getting an animal's abilities from a bite. Raj mused eloquently about inheriting the abilities of a rat in "The Alien Parasite Hypothesis".
Season 1-2, Season 4-5 and Season 8-9 are the only examples where the ending of one season and the start of the next are on the same day, as Season 1 ended with Leonard (Johnny Galecki) and Penny (Kaley Cuoco) going out on a date, while Season 2 started with them coming back. Season 4 ended with Penny and Raj (Kunal Nayyar), while Season 5 started the same day with the guys at work. Season 8 ended with Leonard and Penny going to Las Vegas and Season 9 begins with Leonard and Penny arriving.
Raj talks about going with Emily to see the new Avengers movie. This would have been the second Avengers movie, Avengers: Age of Ultron (2015).