At designer Sy Devore's October 31, 1957 50th birthday party held at Lucy's New Orleans restaurant in Los Angeles with actress Jeanne Carmen
"The party was pretty amazing, even by Hollywood standards. I remember getting excited that a very cute little clown seemed to be flirting with me, until Cliff pointed out that the little clown was Debbie Reynolds
I walked into one of the party rooms and saw a costume that topped them all: Nat King Cole was dressed as Elvis, with a black leather jacket, pasted-on sideburns, and a guitar around his neck. Elvis and I had always loved Cole's music, and I went right up to him and introduced myself. He was extremely nice, and when he heard I was with Elvis, he said he really wanted to meet him. I went to find Elvis, and at first it was hard to get him away from the pretty girls he was talking to. But as soon as I told him who Nat King Cole was dressed as, he had me lead him there. I'll never forget the sight of Mardi Gras Elvis standing there talking to Nat King Cole Presley." - George Klein
Sy Devores 50th birthday party was held at Lucy's New Orleans restaurant in Los Angeles owned by Monte Prosner. Billy Murphy gave Elvis the hand made gold Mardi Gras mask that Elvis is photographed wearing, compelling him to attend. I don't think the theme was Halloween, it just happened that Sy's birthday was obviously always on Halloween.