The trapeze artists
I don't see anything in the IMDB credits about the two trapeze artists who perform in the early garden party scene -- I wondered if they could be these: http://nimblearts.org/ Anybody know?
shareThey are the Stebin Twins (Karyne and Sarah) who work with Cirque du Soleil. Apparently they were teaching Joss Whedon's wife, Kai Cole, how to do trapeze and she suggested they perform during the party scene.
share