I don't really read or write this crossover, but just a thought.
For some reason or another, danny gets summoned to hogwarts. Maybe they summon him to help with voldie, or maybe a student finds an old book in the restricted section about summoning, and they dare their friend to try it.
Whatever way danny gets summoned, he's just a chilled teenager with dorito fingers. So he chills with whoever summoned him, and then they ask if he wants a tour of hogwarts, so they head to the great hall. Opening the great doors, danny is met with his worst nightmare.
Green and red lights hung everywhere, mistletoe was protruding from every crack in the stone, and standing at least 10 feet tall was a giant decorated tree with a shiny star on top that twinkled with magic.
The summoner heard an unfamiliar sound and slowly turned to see danny fucking GROWLING and eyes ZEROED in on the tree, slitted like an animals. Drool was falling from his fangs, and his posture is one of a threatened cat with his back slightly arched and hackles raised.
The summoner had successfully talked danny into not attacking when they heard a new person enter the hall, and as soon as summoner saw who walked in, they knew that they couldn't stop danny.