Hazbin Hotel would be foolish to not have a Christmas Special. Plus, it could be a chance for Charlie to bring out the best of her people. Here's how I personally think HH should have a special like this.
We learn that Christmas is either illegal or very unpopular in Hell. But inside the Hotel, is another story. Charlie has worked her back off to get the place spruced up for Christmas. But the other characters and patients are less enthusiastic. So, Charlie decides to host a Christmas therapy session where everyone explains their relationships with Christmas. We learn that some demons did not have very good Christmases in life, others feel contradictory to their nature, as it involves Christ.
But Charlie explains that Christmas is many things. It has pagan roots, it's about families and friends getting together, it's about fun, silliness, stupidity, generosity, etc. And thanks to this, Charlie is able to brighten the mood of the Hotel, and they agree to celebrate Christmas. The special ends with Charlie singing a song similar to "Believe" from The Polar Express, about how even the damned can find Christmas spirit. As this happens, for some dumb, but heartwarming reason, it starts snowing in Hell, and other demons start hearing Charlie's song, and we see Hell's denizens start doing good things and being generous, except for the three V's and maybe Lucifer.
What would you write?