For me personally, there's no one I'd rather have around at Christmas than a character from the Harry Potter universe. Specifically, I'd love to spend this time of year with none other than Luna Lovegood. The aura she has is just pure joy. From 'Nargles' to the iconic line 'You're just as sane as I am', Luna is an extra layer of magic in an already magical universe.
This is why she'd be amazing to spend Christmas with. You can bet she'd have wacky Christmas traditions that you'd never have heard of and bake eerily specific foods to share with family and friends. Besides, you'd be in Hogwarts after all! Perhaps you could go and feed some Thestrals in the forbidden forest and play hide and seek on the grounds before heading back to the great hall for a Christmas feast.
You truly couldn't beat a Christmas with Luna - despite being a little on the eccentric side, she's a shining light of happiness that would make for the best season ever.