I'm glad I usually sing Jeannie's version of Braes of Balquidder ("The Fair of Balnafannon")

One story I like is of Christie Moore adding the Irish chorus to "Curragh of Kildare" in the early 60s, believing it was Burns song, then some time later finding out it maybe wasn't - I think it's one of the ones in Johnson's Musical Museum that crops up in Burns antholgies, so was probably one of the ones that Burns collected, and may have edited for publication. (and yes, I did think Curragh was traditional in my youth).

I never thought that "Fiddler's Green" was a traditional song, but I always saw it as sitting squarely in the "Unfortunate Rake" tradition, via "The Dying Stockman".

And I don't think I've ever heard Mr Happy sing a tradtional song.