Each scene with Willow/Warren was filmed twice - once with Alyson Hannigan playing Willow and again with Adam Busch as Willow. Which actor performed the scene first depended upon how "Willow" Warren was supposed to be. That is, when Willow first changes into Warren she acts more or less like Willow; in these early scenes Hannigan would act first so that Busch could somewhat mimic her performance. In later scenes when Warren's personality is more prominent Busch would act first. Because of this decision to use both actors, filming the Willow scenes took much longer than usual. In an interview with the BBC, Elizabeth Anne Allen says, "everything had to be so exact." She explains that if Alyson or Adam "gestured or moved their head differently from the other person, they had to do the take over again. So that one scene took us a day and a half to shoot."
Drew Z. Greenberg and David Solomon say in their DVD commentary that the reason there are no potential Slayers (apart from Kennedy) in the episode is because their budget wouldn't stretch to allow for the extra actors.
It's obvious in the first couple of scenes that Sarah Michelle Gellar is suffering a cold. Her voice is hoarse and movements slow, adding a scarf and mug within the dialogue was probably a nod to her feeling unwell without writing it into the script or making it overly obvious to those who miss it.
Although a military committee ordered the Initiative to be filled with concrete, at least portions of it remained intact.
This is the last episode where Tara is mentioned.