This episode's title means "as a friend" in French and also functions as a pun, reading phonetically as "enemy" in English.
The script went through many revisions; several scenes were cut, including one that featured The Cigarette-Smoking Man teaching Scully how to water-ski.
Chris Carter termed this partly successful seduction of Scully by the Cigarette Smoking Man as "the creepiest episode of the year".
William B. Davis came up with the idea of Cigarette Smoking Man seducing Scully with medical knowledge and pitched it to Chris Carter. Both Carter and Frank Spotnitz were intrigued by the idea and especially by the fact that CSM and Scully hadn't had much interaction throughout the course of the series. Davis also relished the opportunity of getting to work more exclusively with Gillian Anderson as they hadn't shared many scenes together.