In My Fair Lady there is more emphasis on Eliza's character developing her speech and going through all the unusual exercises' such as speaking with marbles in her mouth and being hooked up to a machine while saying her vowels, than in the written play. This is probably due to the fact that in the play people should expect all of this to happen and don't need to be told. Also, Cukor's My Fair Lady did this in the musical because it adds entertainment value.
When Eliza finally is able to speak well, Professor Higgins and Colonel Pickering decided to take her to meet Higgins' mother to see how see would behave around other distinguished people of high class society. This is the same in both Pygmalion the play and My Fair Lady the musical, however, in the musical they take her to meet Professor Higgins' mother at a horse race where as in the play they take Eliza to Higgins' mother's house. Also, in the play Eliza meets Mrs. Eynsford Hill, Clara, and Freddy at Higgins' mother's while in the musical she doesn't meet Clara, only Mrs. Eynsford Hill and Freddy at the horse race.
After Mr. Doolittle is made into a wealthy man, which happens in both works, he marries his live-in girlfriend. In the play, he visits Mrs. Higgin's before going to the church to get married where as in the movie he doesn't visit her at all. The first point in the play when you find