In which episode does Alex Krycek first appear?

Alex Krycek first appears in “Sleepless,” the fourth episode of The X-Files’ second season. The episode aired on October 7, 1994, and introduces Krycek as a young FBI agent temporarily assigned to work with Fox Mulder while Dana Scully is absent.

Nicholas Lea played Krycek, who was initially intended to be a short-term replacement partner. The character quickly became much more important, evolving into a recurring antagonist tied to the Smoking Man, the Syndicate, and several major conspiracy developments.

A common mix-up is choosing “Duane Barry” or “Ascension,” because Krycek appears in both episodes soon after his introduction. “Sleepless” is also notable for featuring the first on-screen appearance of the informant X, another important recurring character.