Think with me, Petunia only met James once, and she was trying to forget the memory more and more. Dumbledore, McGonagall and Hagrid had only seen Harry as a baby.
I need a fanfiction where Hagrid comes pick Harry up, takes a look at the boy and goes: "This is not James' son."
Black greasy hair, pale skin, big nose.
The was no deniability, the kid looked exactly like a mini Professor Snape, unless, of course, for the famous scar and the eyes — ah, Lily's eyes! Would it be true? Lily Potter was a cheater?!
I doubt that Petunia would even remember that one neighbor she had as a child, who spent most of the year away, that was just as freaky as the sister she was trying to forget and who she hadn't seen in more than a decade, let anole realize that the kid, who she rather pretend didn't exist, looked like him.
Snape had alittle petty smile on the lips, realizing that James Potter had sacrificed his little life to save not only a baby that wasn't his, but no other than Severus —no, Snivellus' son.
At same time, somewhere in the other side, James was smiling too, when Snivellus' son got sorted into Gryffindor, basically begging to not go to his father's beloved Slytherin.
Rita Skeeter was reveling with the news. The Daily Prophet's machetes spent weeks looking like:
"Young Savior Harry Potter enters Hogwarts with Shocking Scandal!"
"The myth of purity of Lily and James Potter: AFFAIR?!"
"Harry Potter isn't a Potter at all!"
"The Boy Who Lived and the MOTHER WHO CHEATED?!"