I have been to Cirque du Soelil twice and both times was very impressed with what I say. The most recent one, Varekai, made good use of a contortionists, who was very flexible.
I came across this YouTube video today of three girls that start singing about potato salad and then move into an amazing contortionist routine. By way of Boing Boing by way of For your Entertainment.
While it would be easy and snarky to come up with some crude innuendo about how flexible the girls are blah blah blah. That I think belittles the extreme level of athleticism these girls must have been at and the time it had taken to get that good. I just have to say that I have never seen something as amazing as this, Cirque du Soleil included. Once you get past the singing, about a minute in, the fun begins.
Update : Apparently this is the girls are known as the Ross Sisters and this was in the 1944 movie Broadway Rhythm.