I had the same thought about Buffy saying "Oh, balls," which is really a Spike line. Although Joss hasn't exactly been Mr. Consistency on the voices for awhile now - I remember thinking that his X-Men comic tended to lash around using Spike-voice for Emma and/or Wolverine at the same time as he was writing lines for Spike that sounded like Wolverine ("not this girl, not this day"). So I'm not sure how much I should assign to what any character sounds like... which is another reason for me to feel uneasy about this rendition of the 'verse.