Theories & Headcanons

Chapter 1: The Doctor's Name

LEAD-UP/EVIDENCE

Here's the two examples I could find of the Doctor's name:

d³∑x₂ or possibly Delta-Cubed Sigma X-Squared, AKA Change-Cubed Summation Unknown-Squared. From the sources I can gather, at least, so take this with a grain of salt because I am terrible at maths. 

ΘΣ or Theta Sigma, AKA Th and S. Both capitalized.

Since the first was in an in-universe public document, I'm going to assume it's a code or some such, rather than his proper name. However, I find it very interesting that both examples include a capital Sigma.

The Master's name was supposedly Koschei, which is a Russian mythical figure from what I can gather. Perhaps that means that the Doctor's name is human in origin as well.

His name is pronounceable by humans, because River once whispered it in his ear, no matter what he's claimed in the past (The Doctor lies).

Name magic exists in-universe, as seen in at least one episode.

ACTUAL THEORY

The Doctor, for whatever reason, can be controlled by his name. Which is why only River, the woman he loves and trusts most, is allowed to know it — because she wouldn't abuse it, at least not by the time she actually learns it. What's more dangerous than someone in command of the Oncoming Storm? It could as well explain why some villains are obsessed with knowing it.

ΘΣ are his initials. His name, like the letters, is Greek in origin and quite possibly shared with one or more mythical figures (wouldn't it be funny if his first name was Thanatos?).

And that's it, that's my theory. What do you think?

Chapter 2: The Doctor Hates Dresses

Even 13 never wore a dress, as far as I know. No Doctor willingly wore a dress, ever. (Except Fugitive, but she is basically only set up for a spinoff and I refuse to count her).

Maybe he just thinks they look unfashionable, maybe they make it harder to run, maybe he's just not interested in them. Who knows?

That's it. That's the whole theory. 

Chapter 3: The 19th Doctor

The 19th Doctor (who is really the 20th if you count War) will finally be ginger. He will also finally have a lifelong Companion in the form of a cat who was accidentally made immortal... Somehow. He will carry a Sonic Staff instead of a Screwdriver, and will be quite fond of riddles.

He believes that tea and jam on toast can solve anything, and something must be wrong with you if it doesn't solve your problems. He tends to be arrested more than his previous incarnations, and has more trouble controlling his destination. Maybe it's his old age finally getting to him, maybe something's just wrong with this Regeneration, but he tends forget things often and behaves somewhat erratically (you might even call him mad).

His other companions include:

* A repentant Dalek with empathy named March, whom The Doctor does not always get along with (and sees too much of himself in)

* An orphaned Timelord girl who goes by 'The Dreamer', who once had a bad encounter with a TARDIS core that led her to having confusing prophetic dreams.

* A human professor named Lewis, who very much does not want to be here and would like to go home now, thank you very much. (Too bad The Doctor can't actually figure out how to get back to his proper timeline...)

Okay, so more a story idea than a theory or headcanon. But it's a good one, no?

Chapter 4: Another Story Idea Because I'm Bored And Sleep-Deprived

You know how The Doctor from Doctor Who can't tell anyone his name or something terrible will happen? I came up with the idea that it's because knowing his name lets someone have complete and total control over him, like he can't even try to go against what he believes their commands mean even if he finds a loophole (which isn't a Time Lord thing, this affects only The Doctor, for... Reasons). HOWEVER, the one who knows his name has to intentionally use the new bond (which takes about as much mental effort as breathing but still is a purposeful choice) or else it won't register as a command, meaning they could choose to let The Doctor be free and not command him (which is why he felt safe telling River, the love of his life).

This, obviously, would be very bad. The Doctor is the MOST FEARED BEING IN THE UNIVERSE. He is The Oncoming Storm, The Timelord Victorious, The Destroyer Of Worlds, The Imp Of The Pandorica, and about a thousand other really dangerous nicknames. Him without his morals, or being controlled by someone without his morals, could bring the universe to its knees.

He loves and trusts his Companions, but he doesn't trust them quite enough to risk telling them his name (even if they didn't use it, what if they slipped up or were tortured and told someone else?). But what if he had to?

I came up with a fic idea where The Doctor is being mind controlled by The Master in a different way than using his name, using technology that gives him some loopholes and would be hackable given enough time. Unfortunately, he doesn't have time, as he's about to be forced to blow up the Earth. Captain Jack Harkness is caged nearby, yelling at The Master to stop, while the Master just laughs as The Doctor futilely struggles against the machine (succeeding in stalling only by a few seconds).

At the absolute last second, with literally no other hope, The Doctor focuses all his energy on telepathically communicating with Jack, which is difficult as Timelords aren't the best at long-range telepathy (and humans aren't really built for it at all) and he's more-or-less out of practice with no other Timelords to hang out with on a regular basis (he has a psychic bond with his TARDIS, but that's mostly because of her power and is different anyways).

The Doctor briefly scans Jack's mind in the hope his friend has some sort of brilliant hidden plan. He doesn't. Resigning himself to what must be, the narrative briefly makes it seem like The Doctor has given up hope and will just push the button that will blow up the Earth... Only for him to telepathically tell Jack his name and how to control him with it.

Jack uses the name (which he doesn't say out loud, of course, just knowing it is enough) to override the machine controlling The Doctor, making him free them both from The Master. They run, with Jack commanding The Doctor to make sure the machine can't take back over, eventually making it to the TARDIS where they save the day.

Day saved, Jack uses tools in the TARDIS along with instructions the TARDIS helpfully puts up on her screens, to get the machine off The Doctor. The Doctor is resigned to his fate, thinking that at least Jack won't be the worst owner... Only to be surprised when Jack stops using the control. The Doctor is suspicious at first, but they talk and have a fluffy moment where some of The Doctor's trust issues are healed (just a little), and then they hug.

It's a sweet moment... Which is completely ruined by Jack using a wildly inappropriate innuendo.

(Remember that Jack is attracted to just about everyone, likes to greet The Doctor by kissing him, and flirts all the time... He doesn't exactly expect people to flirt back and isn't disappointed — except maybe playfully — when he's turned down/ignored, but if someone flirts back he is immediately ON BOARD.)

Chapter 5: Thirteenth Doctor Rewrite

I like Thirteen's basic character and a few things about her story, but I mostly really dislike canon from her onward. So I sorta just... mentally rewrote her.

Obviously she still has some trauma, the Doctor's always going to. But I like to think of her as the most healed.

After Eight's sacrifice, War's atrocities, Nine's rage, Ten's guilt, Eleven's self-hatred, and Twelve's breakdown...

After so many lifetimes since the war and the personality modifications Eight went with when he became War...

After finding out that Gallifrey is still standing and she never actually killed her own people or destroyed her home...

Thirteen deserves to be happy.

So in my head, she's lighter and goofier. She's finally given herself permission to breathe, to be happy, to explore for the sheer wonder of it again. She's still the Doctor, she's still saving people, she's still got her dark edges and things haunting her — but she's finally at peace with her pasts.

Also, I'm ignoring the Timeless Child because no.