In your case I would direct your attention to Angel episode "Waiting in the Wings" (3.13 Feb 4, 2002). This aired three months after the Buffy musical, and at some point Amy Acker had mentioned to Whedon that she was trained in ballet. So Whedon invented a pretext involving Angel's crew viewing a (supernatural) performance of the the classic ballet Giselle where Alexis Denisof's character would doze off and there would be a comic dream sequence of him as the Prince dancing a duet with Amy. A real ballet dancer had to be cast as the prima ballerina for the "real" performance, and instead of auditioning for dancing, Whedon had candidates read the expository text that character would have to perform that with David Boreanaz before the climax. Summer Glau auditioned, she was 21 years old and had studied to be a classical ballet dancer all her life until at 19 a toe injury forced her to retire. She'd moved to Los Angeles to get acting work and to that point had gotten nothing at all for two years. However, she absolutely nailed the audition and performance, featuring this text:
Ballerina: "There is a section in the first act, during the courtship dance, where - my foot slips. My ankle's turned and - and I don't quite hold - every time. (Glances at the box) He doesn't notice. He doesn't even know ballet that well. But always, at that same moment, I slip. - It isn't just the same ballet. (Looks at Angel) It's the same performance. I don't dance. (Returns to watching the stage) I echo. (After a moment she turns back to Angel) Please - can you make it stop?"
Comic book author Jeph Loeb was in attendance at the audition (there's extensive Whedon commentary about this ep on the DVD) and suggested Glau be invited to read for River Tam on Firefly. The Angel episode aired the day before Buffy ep "Dead Things" (6.13 Feb 5, 2002), which is also about people being controlled, Warren tries to turn his ex-girlfriend into a sex slave with magic technology and when that fails murders her as she tries to escape. Anyway, Glau's performance brought Whedon's own words above to life, and you can see how that text points strongly at the themes to come in both Firefly / Serenity / and Dollhouse, even Eliza Dushku's character name.
