A/N: So, I've been wanting to write this for an unbelievably long time. I was reading Restaurant at the End of the Universe and an idea for a crossover popped into my head because Douglas Adams has just got it like that.

This story begins just after Nine regenerates into Ten and completely disregards the Children in Need special where he tells Rose who he is. It's basically right after Ten says, "Barcelona."

I'm definitely adding one more chapter, possibly two. But anyway, I hope you enjoy this! I was actually somewhat proud of it.

Disclaimer: Doctor Who is the property of the BBC and the Hitchhiker's Guide to the Galaxy books belong to Douglas Adams. I own nothing; this was written only for entertainment purposes.

The Doctor gave a cheery smile and attempted to take a step towards the TARDIS console. He wobbled then frowned down at his feet as if he was surprised to find them attached to the ends of his legs. He took another step. And wobbled.

"Don't worry," he said, waving a hand at Rose. "This sort of post-regeneration disorientation is perfectly normal. At least there's no amnesia this time, that was terribly inconvenient." Rose's eyes widened.

"Wh - what happened? Doctor, is that you?" she said, her eyebrows pulling together, looking very much like a young child who's just been told that Santa Claus isn't real. The Doctor nodded, trying to look reassuring but only succeeded in going slightly cross-eyed. He took a few more shaky steps towards the console and finally managed to grab a lever for support.

"It's called," he said, somewhat coherently, "regeneration. When Time Lords are about to die they do this... thing. This - this process, yes, that sounds better. Every damaged cell in our body turns into a healthy one. But it changes the way we look and talk. I'm still the same person though, just with a few new bits."

Rose took a deep shuddering breath in and stared at this man who was both new and familiar and tried to connect him to the man who had stood before her just a few minutes ago, who had had big ears and cropped hair and a smile that was entirely too bright for his sullen persona. As she breathed out, she counted the ways in which he reminded her of him: his energy, that she could see even now was boundless, his hands that still moved nervously as though he didn't know quite what to do with them, and, most importantly, his eyes, that looked too old for his face and too honest for any human that she could think of.

In the midst of these epiphanies, the Doctor stared blankly at the controls on the console. His vision was blurry and a feeling of heavy-handed fatigue was slowly descending over him. He moved his hands slowly and without his usual natural confidence, still knowing exactly where to press, pull and turn but somehow needing to try harder to access the information that he once used to recall with ease.

Finally, he entered the coordinates, 'Powell Estate, London, England, Earth, December 25th, 2005.'

oooOOOooo

The universe is big. This is a well-documented fact and one that it is quite impossible to refute, as no one is sure quite how big it is, although scientists, reputable and otherwise, tell us that it is infinite. Most minds are completely incapable of fully realizing the concept of infinity and thus, are unable to disagree with any claims about the relative size of the universe.

So, for the purposes of this story, yes, the universe is big.

In an infinite universe, or perhaps a multiverse, it is possible for any number of bizarre coincidences to occur and they almost always do despite the high improbabilities involved. This says something about the nature of the universe. Of course, when an Infinite Improbability Drive is introduced into the equation the most insane and unlikely coincidences will immediately become apparent. Then they will occur.

They occurred.

oooOOOooo

"Three to the power of eighty thousand to one against and falling."

The cool, calm female voice echoed around the TARDIS and made Rose nervous. She couldn't say why, she'd had plenty of experiences with things much more disturbing than disembodied voices but still it unsettled her that a strange voice was reciting mathematical figures at her.

She got slowly to her feet and looked around the console room. Everything appeared to be normal yet she distinctly remembered feeling the sort of strange, jolting sensation that she had come to associate with what the Doctor called "unexpected detours" and she called "crash landings."

The Doctor... where was the Doctor? She felt a hint of panic at the thought of the Doctor being unsupervised in his current questionable mental state. She proceeded to search the console room, occasionally calling his name, as though she actually thought that he might answer. When she finally found him, she almost wished that she hadn't.

He was lying on the floor near the console, clearly unconscious, taking shallow breaths, forehead pale and clammy. She checked for a pulse, which seemed weak but consistent and then turned towards the TARDIS doors with an air of decision. The Doctor was clearly in some kind of trouble so she would go and find help for him. She would later realize that this had been one of the many defining moments in their relationship.

"Three to the power of sixty thousand to one against and falling," said the unsettling voice.

"Oh, stuff it," Rose muttered and pushed out through the doors. She found herself in a room that was the kind of white that seemed to be designed specifically to dazzle and/or blind. There were control panels lining the walls but they didn't seem to be there for any particular reason. All in all, it seemed like a room that was intended to convey the impression of splendor and purpose without actually having any at all.

It was also filled with squirrels.

Rose blinked. She blinked once again for good measure and was forced to conclude that her eyes were functioning properly and the room she was in was, indeed, inhabited by small furry rodents. "Erm, hello," she said to the nearest squirrel, feeling slightly foolish. "Can you tell me where I am, please?"

The squirrel looked at her in obvious disdain, chattered and scurried away, tail flicking in a thoroughly insulting manner. Rose raised her eyes to the ceiling in annoyance and was rather surprised to find that it was looking back down at her. She looked away quickly. Squirrels were at least familiar, if slightly odd in this context. Rose didn't know how to deal with sentient ceilings.

"Three to the power of twenty thousand to one against and falling."

"Alright," Rose said, glad to have found something from which she could reasonably demand some answers. "Can you tell me where I am and how I got here? Because, right now, I have no answer to either question and the person I usually get answers from is lying unconscious in a time machine."

"You are in the Starship Heart of Gold. Anything that you see around you that does not seem to be within the realm of possibility probably isn't. We are working to rectify this, in the meantime, please keep calm. Three to the power of fourteen thousand to one against and falling."

Rose took a deep breath and sat down among the loudly squeaking squirrels, accepting the fact that that was as near to a coherent explanation as she was going to get anytime soon.

oooOOOooo