1. Clara is the Doctor and River’s Daughter (who he forgot about…hence the whole remember and weird timeline stuff since the Doctor and River never meet in the right order-maybe he and Clara don’t either. Also explains the “may be a Time Lord part)
2. Clara is a Time Lord with a fob watch somewhere
3. She’s side effect caused from Rose looking into the TARDIS
4. She’s CAL or has something to do with the library
5, She’s Jenny regenerated
6. Has something to do with the Doctor’s 9th regeneration and he forgot about her (fits with the remember and 50th anniversary stuff)
7.He met her in an alternate timeline and forgot once the timeline was erased (the big bang) and for some reason she sneaked through. (kinda like how Amy remembered the Doctor back into existence)
As you can see, I have many since I really have no idea! I hope at least one of these is kinda right, but knowing Moffat I doubt it!
Thoughts? Or am I completely off?