I think I need more information to make an actual informed guess, but if pressed for an off-the-wall theory at the moment ...

Mine would be that Clara (who I still like to call Souffle) is not human. There's got to be some mechanism by which she can be pretty much the exact same person in the 1800s as she is today, even though she was born to parents and grew up.

There are a few possibilities I can think of that might cause that. First, the Clara we see right now could be the original Clara, the one who was born and grew up and went off on adventures with the Doctor. Something is going to happen in the future that will cause her template, for lack of a better word, to get spread to other times and places. But that doesn't explain how she ends up on people who are going to end up helping the Doctor. It could be something to do with how she's spread about, and who does the spreading, and why they do it. But I'm not sold on that idea at all.

Second, and this idea is even more tenuous, she could have something to do with Rose Tyler. The only reason I say this is because of the death date of Clara's mother on her tombstone in the latest episode. It was March 5, 2005. Since 2005 is the year when Doctor Who restarted, I plugged in the date on Google to see if anything happened then. It was the day that the original episode, "Rose", was leaked to the public in advance of the official airing. I have no idea if that actually means anything, but later in that first season Rose was infused with the time vortex and able to make changes throughout all of time. As far as we know she had no reason to know that she should plant Claras in different places to help a future incarnation of the Doctor ... but maybe it's possible that she could have, if she had a reason that we haven't seen yet. The only reason I give this idea any credence is that Rose is confirmed to be coming back for the 50th anniversary special along with Ten.

But wrapping back to my opening, the bit about Clara not being human, we have my third theory, the one I like best so far even though there's not much to support it and I reserve the right to change my mind as I get more evidence.

In this theory, Clara is not human at all. Not now, not in any of her incarnations. Instead, she's something else (no way to tell what), some being or force that uses a similar system to the robots we saw in Episode 6. The Doctor said that those robots had some sort of psychic ability to make you see what you expected to see, what you wanted to see, which was why one looked like a little girl and a later one looked like the Doctor. This psychic projection robot apparently works well enough that even its master, the lady in the tower, was fooled. It actually sounds a lot like how the Doctor's psychic paper works, too.

If Clara is something else, then when she was "born", her parents would see her as a baby. As she grew up, her parents would see her as a little girl, and the Doctor saw her as such too as he spied on her. The current Clara, the past Clara, the future Clara, could all look the same because that's what the Doctor expects after he saw the first one. They're different versions of this same being, each getting the same image pasted onto it by the Doctor's mind.

One thing that got me thinking along these lines is how the aliens reacted to her in the latest episode. On a number of occasions she got strange looks from the aliens. When they look at her, they'd see something different than what the Doctor sees. And the little girl, Mary, was being chased when she first saw Clara, and whatever she saw on Clara, it made her continue to run away for the first several times. Combine that with Clara saying that she thinks the TARDIS doesn't like her, and maybe you've got something.

But that still doesn't explain how she, or it, or the multiple its, keep showing up where the Doctor needs them. Need moar data.

Also, I think the Question, the one that will be asked that can't be answered, is going to be asking what the Doctor's true name is. We know that River is going to learn this name, but as far as we've seen she hasn't been told it yet. She uses it to convince Ten that she's someone he should trust, but it's possible that River is going to learn this name through some other means altogether. A part of me thinks it's possible that her whole schtick about being super trusted by the Doctor is her own long term fabrication. River started out (from her perspective) trying to kill the Doctor, then saving him, then becoming obsessed with him. If she heard his true name when the Question is asked, and if she keeps meeting younger versions of the Doctor, she could use her knowledge to manipulate him into making sure she's someone he trusts, which in a wibbly wobbly way gets him to trust her when his future incarnations meet her younger self. Maybe.

P.S. Why didn't the TARDIS translate the barking alien's language for Clara? Isn't everything supposed to be translated automatically?