After writing the first draft, Tim Minear had to rewrite parts of the script to accommodate Wesley's arrival and Doyle's departure; the final scene on the rooftop was originally between Angel and Doyle.
The script was originally called "The Killer I Created", until a detailed summary appeared online, prompting Tim Minear to alter the title. "I went on to the Buffy message board... changed the title and said it was about dreams and about horrible things that you do in your sleep, which completely fooled the fans," says Minear.
Elisabeth Röhm and Jeremy Renner would later reunite to play husband and wife in American Hustle (2013).
Title reference: "Somnambulist" is the technical term for a sleepwalker.