La-di-da
adjective
Of or from the upper class of society.
Affecting upper-class or superior airs.
“She was all la-di-da, with her nose in the air, and we were all struggling not to laugh because that would be gauche.”
Synonyms: pretentious, snooty
interjection
(mildly) Expression of disdain for pretension or haughtiness.
“Well la-di-da, aren't you the impressive personage, with a feather in your hair yet.”
Not a care in the world (used in a sing-song voice, for childhood rhymes)