Hogwarts, to welcome you home

"You understand, Professor," Harry began, after a moment, "that I don't have my N.E.W.T.s. I never even finished seventh year. Between everything, I never had a chance the first time around, and then afterwards there didn't seem to be much point. Hermione argued for it, of course, but I was so tired of Britain. So technically, I am completely unqualified for the position."

"Quite a way to begin an interview, Mr. Potter," McGonagall said, dryly.

Or, three years after the war, Harry Potter becomes Hogwarts' newest Defense Against the Dark Arts professor.