Audrey Hepburn, Fred Astaire, Kay Thompson. If you haven't seen it yet, I'll lend you my copy. Or just watch these clips, because these are some of the best scenes from the whole movie!
Kay Thompson "Think Pink" (Her character here is based on Diana Vreeland, the wonderfully crazy editor of Harper's Bazaar and Vogue):
"On How to Be Lovely":
And this last clip doesn't even have Audrey, but this is one of my favorite parts in the movie, so I had to include it:
Kay Thompson and Fred Astaire "Clap Yo Hands":