Jamie mentioned Donald O'Connor in her post for Take This Tune. I remember I always loved him and thought he was undervalued as a dancer. Here he is doing an incredible routine called "Make 'Em Laugh."
And Donald O'Connor dancing reminds me of Gene Kelly whom O'Connor used to dance with all the time. Take a look at the two of them doing a dance medley back in the 60s on the Gene Kelly TV show.
What is amazing is that the audience recognizes the dance steps when one or the other of them begins to dance and they applaud!