Schur said he instructed Carden to prepare for the episode—in which the show's four human protagonists hide in Janet's void, thus rendering them into Janets themselves—in March, four months before the episode actually filmed. The cast started rehearsing the episode earlier than they would have for one with a more conventional script, and those rehearsals and blocking were filmed, so Carden could watch ("1 million times," she says) how the actors moved and spoke—and so the movements could later be mapped for special effects. Carden also made an audio recording of the cast during the table read.
According to Schur, one of the reasons he knew the show could pull off something so challenging was because, "Orphan Black did it 100 times." That being said, both Carden and Schur acknowledged that there were multiple times during filming that the writers and crew would look at each other after shots and ask, "that was fun, but what if none of this makes any sense?"