A high school journalism class exchange from 1986:
Mr. H. (singing:) "Just walking in the rain..."
Me (saying the next lyric:) "Getting soaking wet..." That's Johnnie Ray's "Just Walking In The Rain." I know that song.
Mr. H.: How do you know that song?
Me: I remember...
Mr. H.: ...You remember those days, huh?
Me: No, I've heard it on oldies stations. That refrain is memorable.
Having been on both sides of the "How do you know this before-your-time song?" scenario, I appreciate being asked how I know a song and, as long as I don't sound too schoolmarmish, asking other people where they've heard songs I wouldn't think they'd know. It's fun to share knowledge that doesn't have much of an outlet otherwise.