"WHY can’t a woman . . . be more like a man?” queried Rex Harrison in an early rap classic. (Hey, you kids think you invented talent-free celebrities?) I first saw My Fair Lady when I was 12 and just starting to get interested in what marketing types call the “features and benefits” of gender identity. No wonder I found this particular number a little scary. After all, by this point in the play, Higgins had already changed Eliza Doolittle’s voice, posture, manners, clothing, hairstyle and her habits of mind. There weren’t really that many bits still up for grabs....