The Savior, Child of the Tardis, Son of a Madman
Out in the Universe there is a bright blue box. Inside this box is a fantastical world. Inhabiting this fantastic world is a strange man called the Doctor, an immortal human from the 51st century, a pink and yellow human who isn't really human anymore and the savior of the wizarding world.
But this isn't the start of our story, though when the Doctor gets involved in anything the start of a story is all rather fuzzy.
No. Our story starts on a deserted street, in front of a ruined house, for every story must have a start. This beginning opens with a funny old wizard in bright-colored robes and a pointed hat, holding our protagonist and wondering what he was going to do with a baby. Now, on we go.
Edit: Previously titled Harry raised by the Doctor a.k.a. The Wizarding World is not ready for This