This is the penultimate time that "Soft Kitty" is sung, due to a lawsuit by the daughters of the original composer for using the song without their permission. Even though the lyrics were slightly altered and the lawsuit was later dropped, the song is only heard once more in The Recollection Dissipation (2017).
After filming of this episode, the crew and cast (including guest Laura Spencer) performed a flash mob to Mark Ronson and Bruno Mars' "Uptown Funk" for the studio audience. Briana Cuoco, Kaley's sister and an accomplished dancer, choreographed and participated in the number.
The first time that Leonard is heard singing "Soft Kitty", and also the first time it is sung without interruptions.
It is revealed that Sheldon realizes he likes Taylor Swift. When he quotes her by saying "haters gonna hate, hate, hate, hate, hate", he references her song 'Shake It Off'.
Title Reference: Sheldon wants to reach his optimum anxiety level to improve his work performance.