The TARDIS had other plans besides bringing Jack back to life. Spoilers:
Set after season 5 Buffy, and during The Parting Of Ways for Doctor Who Season 1. Disclaimer:
I don't own either Buffy or the Doctor. They belong to their respective creators.
She had tasted like the stars, like a million falling galaxies. He could still taste them, and couldn’t tell if it was her or the heart of the TARDIS that was on his lips. “You looked into the time vortex, Rose, nobody is supposed to see that!”
So long he has lived, so long he has traveled. All the people he has met, and there had never been anyone quite like her. Standing on Satellite 5, in those last moments, he had resigned himself to fact that he was going to die. He was a Time Lord, a supposed God, but everything has its time, and everything dies. But not her, not this time. Sending Rose away was the most difficult decision he has ever made, and the easiest.
He couldn’t watch her die. And in some ways that made him a coward.
But she couldn’t leave well enough alone, could never leave well enough alone.
The Doctor gasped in pain, could see the gold dust leave his body, could feel it coursing through his veins. So little time left.
By looking into the heart of the TARDIS, and absorbing the time vortex, Rose had set herself up for either madness or death. Neither of which were futures the Doctor was willing to consider for her. “How can I let go of this? I bring life…The sun and the moon, the day and night... but why do they hurt?”
She had stood there, bathed in yellow light, blonde tendrils of hair lifting on a wind of gold dust. Tears had coursed down her cheeks, and her eyes had glowed like a dying sun. She looked like a goddess, come to life. And seeing her there, his Rose, his companion, seeing her there even after he had sent her away to live, he felt as if one of his hearts would break. “What have you done?”
He brought his hand up to his lips and closed his eyes. The Doctor didn’t know if he was ready to die. It was an inevitability, he knew that. Nothing could change that, not Rose, not the TARDIS. She couldn’t bring him back like she did to Jack. Everything dies.
He adjusted some controls, felt the planets and years spinning past them while she lay unconscious on the floor, while he began the process of death.
The look in her eyes when she brought Jack to life. “I bring life…”
The feel of her lips as the time vortex flowed from her body into his.
The tears that leaked from her eyes as she destroyed the fleet of Dalek ships. “You are tiny. I can see the whole of time and space, every single atom of your existence, and I divide them.”
He didn’t have much time left. The Doctor looked down as Rose began to stir.
He stared at her sadly as she looked around in confusion. That confusion morphed into horror by the time he was done talking.
“Time Lords have this little trick, it's sort of a way of cheating death, except, it means I'm gonna change. And I'm not gonna see you again, not like this, not with this daft old face…” “Everything must come to dust. All things, everything dies.”
As one Doctor died, and another was made from his dust, something was changing far below them.
The time vortex had flowed from Rose to the Doctor to Earth. It had flown past hundreds of thousands of years, into the year 2001.
6 feet below the surface, it settled.
146 days after the death of the Slayer, Rose Tyler brought her back to life.
Green eyes opened and a body gasped for air before clawing its way out of its grave.
Initial confusion passed, and Buffy Summers knew so much more than she should have about the world, about a little blue box and a strange man with many names, and just as many faces.
And standing above her grave, hands bleeding and dirt on her face, she smiled. End.