Sarah Michelle Gellar aparece en el episodio final de la serie interpretando a la propia Buffy:
https://www.youtube.com/watch?v=ngy7FeevuGI
Artículo sobre lo que dice uno de los showrunners:
Sarah Michelle Gellar Guest Stars in 'Big Bang Theory' Series Finale: How This Surprise Happened! (Exclusive)
Steve Holland: I mean,
Steve and I are both big Buffy fans -- as are a lot of people in the [writers'] room. And rather than going for whoever is the hot “right now” celeb, it seemed like a really cool, nerd-pull for these characters who have been fans of Buffy forever too. And it was our way to get to meet her before the end. [Laughs]
How did you ask Sarah to guest star in the episode? Did she say yes right away?
SH: Well, Chuck spoke to her, but it’s always a good sign when the first thing people say is, "Our family are huge fans of this show!" That was how it went with Sean Astin too. We reached out and he’s like, "Our family are gigantic fans, we watch every week!" So then it’s like you’re pretty safe and then it was just a matter of working out scheduling [with Sarah.]