amused
The gala was famous because of Marilyn Monroe's rendition of "Happy Birthday Mister President." Sung in a sultry voice, Monroe sang the traditional "Happy Birthday to You" lyrics and continued the song with a verse from the Bob Hope song "Thanks for the Memory", for which she had written new lyrics specifically aimed at Kennedy.
Thanks, Mr. President
For all the things you've done
The battles that you've won
The way you deal with U.S. Steel
And our problems by the ton
We thank you so much
Afterwards, President Kennedy came on stage and joked about the song, saying, "I can now retire from politics after having had Happy Birthday sung to me in such a sweet, wholesome way." This was probably in part a reference to the dress Monroe wore, which was sheer and flesh colored with 2500 rhinestones sewn into it. The dress was so tight-fitting that Monroe had to be literally sewn into it; she wore nothing under it.
The song and Monroe's performance have been remembered for numerous reasons. First, it was one of her last major public appearances (Monroe died August 5, 1962). In addition, there are persistent rumors that President Kennedy and Marilyn Monroe had had an affair, giving Monroe's performance another layer of meaning.
Below is a YouTube video of the event:
Coincidentally, it was also on May 19th (in 1994) that Jacqueline Kennedy, then Jacqueline Kennedy Onassis, passed away in New York at the age of 64, of Non-Hodgkins Lymphoma.