Fred Astaire. Judy Garland. "We're A Couple of Swells." Written by Irving Berlin. From the MGM classic Easter Parade.
I was actually poking around, looking for a YouTube of the title song... no such luck -- but here's what I stumbled on instead.
I had this soundtrack on vinyl, believe it or not. It was part of a double album, paired with the soundtrack to Singing in the Rain. Wore the grooves out on both discs. And I had every single word and lyric memorized.
This bit -- totally charming and endearing. The likes of these two greats (plus the composer!) we'll never see again, as they don't make 'em like this anymore... so enjoy.