The best last-minute party games use things people already have: a phone, a browser, and a shared screen. You should not need printed materials, a deck of cards, accounts, or a long explanation.
Fast ideas
Start a random word-guessing round and let everyone race.
Create a quick category board from topics everyone knows.
Use a mini crossword when the group wants a quieter challenge.
Play a clue-ordering round when the group wants discussion and jokes.
The no-prep setup works because the shared screen replaces the table and phones replace materials.
How to make it feel hosted
Put the host screen on the TV, read the room code out loud, and start with a low-stakes practice round. Once everyone understands the flow, use a custom puzzle about the group to make the second round land.
Host setup: create a lobby, choose or build a game, cast the host screen to a TV, and have guests join from their phones.