Half Human.
(This is a little fun with the TV Movies half human theory. This is not canon or anything like that, just a mess around/joke. Side chapter to my story 'Frozen In Time')
Enjoy.
The Doctor and Elsa sat in her study in silence. So much had happened over the last few days, she and her guardian...or guardians had defeated the Daleks, saved her home, her people. But what struck her the most is...she had died! She had sacrificed herself to save the Doctor from Extermination, and was struck by the deadly ray. But the Doctor's and Anna's love revived her, gave her a second chance at life.
"Doctor...so much has happened over the last few days." Elsa said quietly to the Doctor.
"Indeed it has Elsa" The Doctor replied not looking at her.
"I still don't understand...why did you save me?" Elsa said getting up and sitting down next to him.
"I have my reasons Elsa, firstly I am your guardian, yours and Anna's protector. It was my duty." The Doctor said turning his head slightly towards her. She smiled.
"What are the other reasons?" Elsa said now curious. The Doctor suddenly looked nervous.
"I'm...half human...on my mother's side." The Doctor said simply, then got up to look out the nearby window. Elsa looked totally confused, she got up and stood next to him.
"Doctor...I haven't got the faintest idea what that is supposed to mean." Elsa said starting to get slightly irritated.
"Don't you see Elsa? The powers of regeneration are in your body, your cells regenerated once, and once only. It cannot happen again. But those cells can be passed on to another generation. My father was a Time Lord, my mother was human...look into my eyes...look hard...and tell me what you see." The Doctor said gripping her wrists and holding them in his. Elsa did what he asked and looked into his eyes.
"I'm sorry Doctor, I don't see what you're talking about." Elsa said giving up hope.
"When a human mother has a child with a Time Lord father, that child is half human with Time Lord abilities. Look Elsa...look...hard!" The Doctor said fiercely. She looked again, and paused...there was something...familiar about them! Wait...no..they couldn't be...could they? My eyes!
"I'm half human...on my mother's side!" The Doctor repeated. Elsa's jaw dropped like a stone. Reality hitting her in the most shocking, breath taking way...she...is his mother!