The episode features the first reappearance of X, who had been murdered in the season four opener "Herrenvolk". This idea was proposed by executive producer John Shiban, who also helped Gilligan storyboard the episode. He explained, "We had the board set up and ... and there was a piece missing and we just couldn't come up with a how to get out of this situation, why doesn't this assassin just kill The Lone Gunmen? It was a flashback story and it was in 1989 and we were pacing around in my backyard, and ... I just turned to him and said, 'X! ... X has another agenda! X is the assassin, it's not some other character, it's our X. ... He wouldn't kill the Gunmen, 'cause he's trying to help Mulder.'"