A/N: Thanks to the wonderful efforts of servant123 and Tsuta-chan, the chicken story has been located! It's the chapter "Gallus Domesticus Gallus" in The Great Escapes of Camelot by beingbored. As thanks (and because this headcanon is shorter than this author's note), I'm posting two chapters today. Enjoy!
In the third Harry Potter movie in the Three Broomsticks, a wizard is using wandless magic to stir his tea and is reading A Brief History in Time.
I firmly believe this was Merlin.