Cut to the end of "The Parting of the Ways"
"I might never make sense again! I might have two heads. Or no head!"
The Doctor laughs as Rose nods with a bemused innocent smile on her face.
"Imagine me with no head! And don't say that's an improvement..."
The Doctor's laughter slowly dies as he continues his explanation
"But it's a bit dodgy, this process. You never know what you're gonna end up with-"
Suddenly, he cries out in a blast of golden light. He clutches his stomach before collapsing against a nearby coral. Rose rushes forward, full of concern.
"Doctor!"
She tries to examine him, help him in whatever way she can as the Doctor winces in pain.
"Doctor, tell me what's going on."
"I absorbed all the energy of the Time Vortex, and no one's meant to do that!" he jokes half heartedly
Rose stares at him with concern as his breath starts slowing down.
"Every cell in my body's dying." He almost whispers
Rose is heartbroken. She starts holding The Doctor's hand whilst cradling his head with her other hand.
"Can't you do something?"
"Yeah, I'm doing it now! Time Lords have this little trick, it's... sort of a way of cheating death. Except..." He looks into her tear-filled eyes. "It means I'm gonna change."
Rose shakes her head slightly, not understanding exactly what this means.
The Doctor continues. "And I'm not gonna see you again. Not like this. Not with this daft old face." He laughs, trying his best to reassure her. "And before I go-"
"Don't say that!" she cries
"Rose..."
"…"
"Before I go, I just wanna tell you, you were fantastic. Absolutely fantastic."
The Doctor gives her a big proud smile to give her something to remember before he can move on. This life was born from blood and genocide, but it was people like Rose who was able to thread it with the love and value he deserved. He begins to close his eyes and let go before coming to one last realization.
"And d'you know what?"
The Doctor's face slowly grins as he stares out into space. He started to well up in happiness as he could finally accept:
"So was I."
The Doctor closes his eyes slowly. His last breath escapes his body. Rose could've sworn she heard "Tha-" for "Thank you" or possibly even "Fa-" for one last "Fantastic". Before she can ponder the Doctor's last words, A calm golden light started flowing from the Doctors body. It glittered and span and danced it's way across the Tardis with an almost childlike bliss. Rose staggers backwards, partially shielding her eyes from it's warmth and beauty. She stares transfixed, as gradually, the Doctor's hair lengthens, his face changes. Eventually the energy slows down and dims before fading away peacefully, and a completely new man is stood before her.
"Hello"