Throughout a long line of vampire slayers and, battling countless supernatural threats, saved the world... a lot.
Buffy Summers wasn't alone in her endeavors, though. She was consistently aided by her Watcher, Rupert Giles (Anthony Stewart Head), and two best friends: Willow Rosenberg (Alyson Hannigan) and Xander Harris (Nicholas Brendon). Together, they became affectionately known as the Scooby Gang. They were further ed by a revolving door of other allies. Regardless, it was that central trio which most frequently fought by Buffy's side. Despite the character's commitment to helping his friends and ing the cause, however, there was actually a classic adventure that Xander Harris took no part in whatsoever.
The installment in question was Buffy the Vampire Slayer season 7, episode 7, "Conversations with Dead People". Written by popular Buffy scribes, Jane Espenson and Drew Goddard, the adventure saw the group divided for a series of titular conversations. Buffy herself was psychoanalyzed by Holden Webster (Jonathan M. Woodward): a former classmate-turned-therapist-turned-newbie-vampire. Meanwhile, Willow, Dawn (Michelle Trachtenberg), and Andrew Wells (Tom Lenk) all interacted with disparate forms assumed by Buffy the Vampire Slayer season 7's Big Bad: The First Evil. Even Spike (James Marsters) was wordlessly present. Despite being still officially credited, however, Xander was nowhere to be seen.
According to an old Willow and Xander's stark introduction to the world of the supernatural. Equally, it started a Whedon trend of surprising, tragic character deaths. As such, Xander being reunited with his long-lost best friend would've marked an emotional moment in the character's journey, even if it was ultimately a ruse.
In the end, the plan never came to fruition. This was likely, in part, due to scheduling issues. Such was why Anya (Emma Caulfield) was similarly absent. According to DVD commentaries, it was intended that the reformed vengeance demon would be visited by Halfrek, before actress Kali Rocha became unavailable. Likewise, Balfour was busy garnering credits elsewhere that year. Furthermore, the real-time nature of the episode meant that only a set amount of conversations could take place – lest any of them be robbed of emotional merit. As such, it was decided that the time would be more emotionally spent having The First torment Willow by evoking Tara (Amber Benson) via the body of Cassie Newton (Azura Skye).
Ultimately, Xander's absence did nothing to disrupt or lessen the episode. Arguably, trying to shoehorn him in for the sake of it would have done that. Therefore, fans have largely not minded or failed to even notice at all. As for Brendon, much like when Buffy was turned into a rat in season 2, it was probably a welcome relief to have a rare break from tireless filming. Besides, in the grand scheme of things, it was kind of balanced out by there having been two versions of Xander in Buffy the Vampire Slayer season 5, episode 3, "The Replacement".