When I first read the OP's original post, I pretty much dismissed it. I think there are plenty of people who are looking for something to offend them. Then I listened to the wav file and I heard the words. However the phrase sounds odd, and I'm pretty sure it's an unintentional result caused by various sounds being accidentally mixed together.
Than I read this from the OP:
The lyrics of the song 'I feel pretty' are the same as those that were sung in the film originally. 'Gay" had a different meaning back then. .I remember the words in the film back in 1961- they were sung as they were written. The word gay is appropriate if you listen to the lyrics that preceded it. I have an old video of a stage show and the lyrics are the same.Gay does not mean lesbianism as you have mentioned.
When I read the post by Bruce, I was laughing, as he intended. He was clearly writing tongue-in-cheek. It was easily recognizable and I can be very slow to pick up subtle things (refer to my posts in the "gay friendly movies" thread). If the OP couldn't see the true intent of Bruce's post, than I understand why he believes the offending phrase was inserted intentionally.
BTW, have you heard the xmas carol with the offending lyrics: "Don we now our gay apparel." Apparently this had been going on for some time.