It was executive producer Douglas Petrie who first broke the news that the season would use a carnival as its primary setting. 
The official main cast for season four of American Horror Story was announced at the San Diego Comic-Con on Saturday evening, July 26th, 2014. 
Ryan Murphy revealed that AHS veteran actress Sarah Paulson would be coming back around for a fourth time, although now she would be working "double" time as she takes on the role of conjoined twins Bette and Dot. The first official photo still from the set revealed a back-shot of the twins wearing a hospital gown staring out of a window. 
Jessica Lange was one of the first cast members slated to return for season four. It was revealed by series showrunners that she would once again be taking on a leading role, this time playing a German expatriate, who is the manager and recruiter of one of the last traveling freak shows in the country. 
It was announced on the final night of PaleyFest that former The Shield and Vegas actor Michael Chiklis would be joining the cast of American Horror Story. Chiklis' character, Dell Toledo, is the former husband of Kathy Bates' character, Ethel Darling and the father of Evan Peters' character, Jimmy Darling. 
The song that Elsa Mars performs on stage, which Gloria Mott refers to as "caterwauling", is "Life on Mars?" by British pop star David Bowie. The presence of the song in this episode is anachronistic as the story is set in the late 1950s and the song was not released until 1971. It first appeared as a single and was also on the album, Hunky Dory.
Perceived blooper: Elsa Mars' rendition of "Life on Mars?" may be construed as a blooper to some as the song was not released until 1971, however its inclusion in this episode was actually intentional. Who's to say that David Bowie didn't rip the song off from Elsa?