I’ve regularly had last-minute (waaay past organising deadlines/turkey ordering/shopping limits) guests for Christmas.
Usually my step children. Worst year was when I had just had my third dc - he was 4 months old, and I had two older dc with severe SN to deal with. Christmas was supposed to be just us (me, exH, 3dc and my uncle who always stays).
A week before Christmas exH announces that my (adult) dsd is now coming to stay. Ok, whatever - a scramble(my problem, obvs, as exH faaaar too busy and important to sort out his own children), but just about doable.
Then 3 days before Christmas, exH casually drops in that my (also adult) dss is now coming along too. Oh, and he’s now vegetarian. And is bringing his coeliac vegetarian girlfriend along too.
3 days to totally reorganise the whole menu, sort presents and stockings (everyone who stays in my house over Christmas gets a stocking, and I’m bloody good at them so didn’t want a last-minute rush job being crap), with 2 dc with SN, so visiting actual shops a huge problem especially when busy, and a non-sleeping baby (ds woke every 45 minutes through the night - literally)
Not quite ringing the bell in Christmas Day, but not far off.