My favorite theories about Oswald Oswin Clara (not in any particular order):
-> She’s the TARDIS.
-> She is Romana.
-> She is the Key of Time.
-> She is the first wife of the Doctor (Susan’s grandmother).
The theories that I dislike or or I don’t think they are possible:
-> She is a regeneration River.
-> She is the daughter of Rose (or Rose itself).
-> She is the daughter of Jack.
-> She is a regeneration of the doctor’s cloned daughter, Jenny.
Just imagine if NASA made/painted a rocket that looks like a TARDIS and sent it to space. They could even call it that.. or Doctor, idk. ohh! And the astronauts would wear doctor stuff like bowties and colorfull scarfs over their space suits! DO IT DO IT DO IT