So I am watching the Futurama Christmas episodes, as I do every year. Xmas Story and A Tale of Two Santas.
But I was vaguely remembering another episode with Santa Claus. Something about Santa becoming good, except that it is a plot with the Robot Devil and President Nixon to do something nasty. I couldn't find it on my DVD collection, which is complete
Finally, it hit me. Futurama #6, from the comic book series.
(Speaking of which, I'll watch the Simpsons Christmas episodes on Christmas Eve as I wrap presents etc.)