This is a really great episode to look at performance and character.
Buffy the Vampire Slayer spoilers follow (for 4.16, “Who Are You”)
Sarah Michelle Gellar is rarely thought of as a great actor, but this (and several other later episodes) reveals her as being capable of great performances. After playing Buffy for 4 years at this point, Gellar is able to completely drop the physical and vocal signs that have acquired the meaning of “Buffy”, and assume those used by Eliza Dushku to play Faith. She is able to fully sell the idea of a different character with the same face.
Dushku does not manage to do the same thing. She is able to partly reduce the ticks and body language that signifies “Faith”, but not completely. Her voice does not bear the strength and playfulness that signifies “Faith”. But she does not at all manage to appropriate Gellar’s voice tone or physicality. She manages - just about - to not be Faith. She does not manage to be Buffy. Instead, we have this new person who looks like Faith, and claims to be Buffy, but is neither. It’s this weak voiced, bland complainer.
It almost ruins the episode. As it is, Gellar’s performance saves it.
