Christmas without Santa Claus? Impossible, you say.
Well, there was a book that was adapted into the 1974 Rankin-Bass special, The Year Without a Santa Claus. Told from the point of view of Mrs. Claus (Shirley Booth, ex-Hazel, in her final performance), it seems that after a routine physical examination, Santa (Mickey Rooney) is convinced by his doctor to "change his routine". So, Santa goes on vacation, leaving two of his elves to try to pick up the slack with just one reindeer, Vixen.
Of course, that spells trouble, and the introduction of fan favorites, the Miser Brothers (Dick Shawn & George S. Irving). This is also a rarity in that the incomparable Paul Frees, usually present for a R-B special, isn't in the cast of this one.
Note that I said this was based on a book, which, to be honest, I'd never heard of. Good luck finding it in a library.