Freelance writers Kenneth Biller and Chris Brancato pitched the idea for this episode to series creator Chris Carter under the title of "The Girls from Greenwich", with the focus being on genetic experiments conducted on sets of twins [REF].
The producers initially looked for twins to play the roles of Teena and Cindy in Los Angeles, but child labor laws made using children from there so difficult that they instead searched locally in Vancouver, finding Erika and Sabrina Krievins [REF].