When introducing a clip of Cyd Charisse early in the film Fred Astaire says "Cyd Charisse. Lovely Cyd Charisse. How she dances." A little later Gene Kelly says exactly the same line when introducing another clip of her.
It was Fred Astaire's idea that he and Gene Kelly perform together in a new dance number in the film. Astaire was afraid that if he and Kelly just stood around and talked to each other, the audience would think they were too old to dance any more. At the time, Astaire was in his late 70s and Kelly was in his mid 60s.