... and one that will change the course of Who forever!
No, it won't! Stop pretending this is more than another episode of Doctor Who, Moffat! It won't change anything significant and even if it does it won't be forever, it will be for this one episode and then everything's back to normal at the end of the christmas special.
If there's a forgotten Doctor, so what? That only changes the numbering of the ones that came after him, it won't affect the course of Who, only merchandise and wiki pages.
I'm not even sure what's so interesting about the Doctor's name, do we really care? Unless it's Hubert Rani-son or Master-cousin Johnson it doesn't matter.
Fine, he has to answer and can't lie, what happens?
Clara: What's your name?
Doctor: Jo'nh Thmis!
Clara: John Smith?
Doctor: No, Jo'nh Thmis!
Clara: Ok, next question, who's the hottest, Vastra, Jenny, River or me?
Doctor: Vastra, but honestly, the guy over there beats all of you, right?
Clara: Eww, he looks like a walking potato ... I think he heard me ... we have to get out of here!