A/N: I'm thinking of getting a patent. I'm quite proud of this.

"Parallel world Doctor..." Rose rolled the words off her tongue as she laid down to bed. She tasted them as she woke up, tried them out as she went down for breakfast. It ended up as a few curse words as she took another wrong turning, but returned to the same three words as before when she found the right route. (Stupid father, stupid mansion. But who was she to complain?)

"Parallel world Doctor." Rose flicked the kettle on, ignoring it as it began to wish her a very happy morning in an overly cheerful voice. "Parallel world Doctor."

He wasn't quite the same, she knew that. He wasn't, and he never would be. She'd never see her Doctor, the old Doctor, ever again. She had the replacement, in a parallel universe, with just the one heart and no time machine.

But as she watched him stroll easily into the large kitchen, obviously following his nose, and offered her that usual easy grin - she thought she might not mind so much. She hadn't fallen in love with him because of the TARDIS; that was just an added bonus. One that she could live without so long as she had him.

"Hungry?" she asked, but she'd barely got the word out before he was headed for the jam. Rose laughed - he wasn't so different.

Two very messy breakfasts later, the Doctor left to shower after pressing a decidedly sticky kiss to Rose's head. She pulled a face but couldn't hide her smile, turning as he left to dump their plates in the dishwasher. In his absence, her mind strayed back to those three words she'd been thinking about before. It was impossible to say why, but they were sticking in her mind like glue and had no intention of leaving. Perhaps it was because her mind persistently strayed to the real Doctor, the one who'd had to leave her behind again - or perhaps it was because it was such a long name that had to be used to distinguish the two Doctors in her mind. It wasn't even especially fun to say.

No, she needed a better name for him. To his face, it would probably always be Doctor – but she needed something to tell them apart in her thoughts.

"Parallel world Doctor," she mused, flicking the tap on and lazily making patterns in the falling water. Time for some experimenting. "Doctor mark two. Oh, god, no... Doc? John? Oh, no way." That would never work. "Um..." She continued in this vein for some time, breaking off only briefly when Pete came in to ask her if she was alright, or if she wanted medical attention.

Having found no success in varying avenues, Rose decided it was time to go back to basics. "Parallel world Doctor. Parallel Doctor. Parallel... Doctor." Extra emphasis wasn't helping. She flicked the tap off again and began to pace around the room. "Para-Doctor. Parallel Doc. Para-doc." She grinned wildly. "Oh my god, para-doc!" She headed for the door, prepared to ransack the entire house to find the elusive Time Lord - but crashed into him as soon as she left the room. "Para-doc!" she exclaimed as she stumbled back, her entire face alight. The Doctor blinked at her in confusion.

"Right, yeah, got it. Er - what?"

"Para-doc!" Rose's face fell when the Doctor failed to understand the flawless logic that had brought her here. "You know, para-doc! Parallel Doctor! And it makes sense, see? Para-doc, sounds like paradox, which is what you are!" She grinned again, plainly proud of her own genius.

The Doctor looked at her with a stunned, blank expression for a moment, before the sides of his mouth began to creep up in a badly suppressed smile. Still, he tried to maintain composure. "Nicknames are very domestic, Rose," he said sternly. "I don't do domestic." The mere fact that he was here, in her house, standing outside her kitchen, was a contradiction to that - and she knew it. Her grin was teasing now, but still jubilant, and the tip of her tongue was sticking out between her teeth.

Having completely failed to rain on her parade, the Doctor could do little more than watch as she practically danced away, and he knew he wasn't going to hear the end of that one. Ever, probably.

Still. Paradox, para-doc. He gave up the pretence and grinned broadly as he let himself out of the back door, stepping into the garden where the rising sun bathed his face and began to dry his damp hair. Para-doc. He rather liked that.