OK, I spent 3 1/2 months in hospital, so I'm on this! The goal is to keep it *really* simple. Don't bring more than you actually need. Here are my pro tips:

- instead of slippers, wear ankle socks with little grippy rubber things on the sole; slippers will get shoved under something and maybe lost when they clean your room in the morning, while you can just keep the socks on your feet

- a backup battery and cable to charge your phone, because there might not be an outlet in reach

- earbuds for your phone so that you can listen to music, watch shows, or have calls without disturbing other patients (ideally with a case)

- unless contraindicated for the surgery (mine wasn't in the groin area), pyjama pants or track pants and a tee-shirt are better than a bathrobe -- you can just keep them on all the time

- a fanny pack, so that you can bring your phone and wallet with you whenever you leave the room (and keep them together); you can clip it around the railing of the bed or stretcher if you don't want to wear it

- an e-reader if you like to read books (and don't want to use your phone)

- hospital food sucks, so also some snacks and/or treats

That's it! Because I was in for the long haul, I also had my own teapot and loose-leaf tea near the end (when I was finally allowed to move from the bed to the wheelchair without supervision), but something like that would be overkill for just one night.