Christmas Trivia Time - What were the boys of the NYPD choir really singing ?

With all the discussion on various blogs (Cassilis gives the best example) of the BBC supposedly banning the use of the word "faggot" in the Christmas classic "The Fairytale of new York", it gives me an opportunity to recount something I learnt only last year when watching a documentary about The Pogues and how they came to collaborate with Kirstly MacColl.

The funniest part for me was the group recounting their video shoot in New York. Not only were most of the group drunk, not only was Shane McGowan almost arrested when they filmed inside a real police station, but the NYPD choir did not sing Galway Bay. Indeed, the NYPD choir did not and still do not know the song "Galway Bay". The video director asked them if there was a sing they all knew the words to and could sing in unison to, and there was.

"Whose the leader of our gang
the one for you and me ?
M.I.C.K.E.Y. M.O.U.S.E"

As one of the Pogues said, if you look closely at the video you can even see them mouthing it.

There we go, some real Christmas trivia to bore the family with.