So, the week before last I was watching the first few episodes of an anime that was new to me, TWEENY WITCHES, when I was struck by the closing song. Obviously a recasting of a famous song, but I couldn't place it, between the changes they'd made and the distracting fact that the lyrics were in Japanese, which I don't speak. And, as is the way of such things, the tune got stuck in my head, where it repeated over and over.
By the next day I realized I'd been on the wrong track: it wasn't a popular song but something classical. I would almost have said it was the Blue Danube Waltz, except that it wasn't a waltz, being in 4/4 time.
Finally I broke down and listened to some samples of the Blue Danube on Itunes to refresh my memory and confirmed that this was indeed the original source of the anime tune, which had been given the title of "DuDiDuWa lalala". And while they hadn't quite given it the Walter Murphey treatment, they had changed it to 4/4.
Live and learn.