Merlin/Harry Potter Crossover Fic
I'm looking for a crossover fic that I can't find, I don't know if I'm confusing two different fics but this is what I remember:
It's modern time and Merlin is a very old man working as a professor, he realizes it's time and turns himself into a child to attend hogwarts.
Another thing I remember is that Merlin and Draco become best friends, and I think eventually become friends with Hermione, too.