As Rose watched, half hidden by a pillar, the man who had replaced the Doctor rushed around the console.

"6 pm..." he said to himself, "Tuesday... October... 5006... On the way to Barcelona!" He turned to Rose, looking incredibly pleased with himself. "Now then... what do I look like?" Rose didn't get a chance to answer before he held up a hand, shaking his head. "No, no, no, no, no, no, no. Don't tell me." Rose watched, uneasy and confused, as he started to pat himself down.

"Let's see... two legs, two arms, two hands..." He twisted his wrist around. "Slight weakness in the dorsal tubercle." His hands flew to his head and he grinned delightedly. "Hair! I'm not bald!" He ran his hands through his hair. "Oh, oh! Big hair!" His fingers found his sideburns. "Sideburns, I've got sideburns! Or really bad skin." Rose blinked as he slapped his stomach. "Little bit thinner... That's weird." He shrugged. "Give me time, I'll get used to it." He rolled his shoulders and paused, his whole face lighting up. "I... have got... a mole. I can feel it. Between my shoulder blades, there's a mole." He rolled his shoulders again. "That's all right. Love the mole."

Rose was close to hyperventilating by the time he finished his assessment of himself and turned to her. He didn't seem to notice, just grinning as he faced her.

"Go on then," he said. "Tell me. What do you think?"

"Who are you?" she asked at a near whisper. His entire face fell.

"I'm the Doctor," he said, blinking.

"No," Rose said, shaking her head. "Where is he? Where's the Doctor?" Her voice rose angrily. "What have you done to him?"

"You saw me, I... I changed." He pointed over his shoulder. "Right in front of you."

"I saw him sort of explode," Rose countered, "and then you replaced him, like a... a teleport or a transmat or a body swap or something."

He looked completely lost for words as she approached him slowly. An arm's length away, she stopped, reached out and pushed him. He rocked back.

"You're not fooling me," she told him. "I've seen all sorts of things. Nanogenes... Gelth..." She eyed him warily. "Slitheen." He raised an eyebrow as her eyes widened. "Oh my god, are you a slitheen?" She looked away, muttering to herself. "How the hell do I explain that to the Emissary?"

The Doctor opened his mouth, then closed it again, deciding it was probably better to not address the Emissary thing at the moment. He went for the other thing that stuck out. "I'm not a Slitheen."

Rose glared at him. "Send him back," she shouted. "I'm warning you, send the Doctor back right now!"

Rassilon, this wasn't going well. He leaned forward earnestly. "Rose, it's me," he said, trying to make her believe him. "It's, honestly, it's me. I was dying. To save my own life, I changed my body. Every single cell, but... still me."

"You can't be," she whispered.

He suddenly had an idea of how to convince her. "Then how could I remember this?" he asked, walking towards her. "Very first word I ever said to you. Trapped in that cellar. Surrounded by shop window dummies... oh..." He looked away, smiling reminiscently. "Such a long time ago. I took your hand..." He reached for her hand and, hesitant though she was, she let him take it. "I said one word, just one word, I said... 'Run.'"

"Doctor," Rose breathed as met his eyes, something clicking in her mind. This really was the Doctor. He grinned.

"Hello," he said. She heaved a sigh of relief, stumbling back against the pillar as the Doctor ran around the console.

"And we never stopped, did we?" he asked excitedly. "All across the universe. Running, running, running..." He flipped a few switches before straightening up and smiling. "One time we had to hop. Do you remember? Hopping for our lives." Rose noted absently that this new Doctor was far more energetic than the last as he started hopping in place. "Yeah? All that hopping? Remember hopping for your life?" He faltered when she didn't react. "Yeah?! Hop? With the..." He stood still. "No?"

Rose considered him for a second. She wanted the old Doctor back, and beyond that, she didn't really want to go back to the Emissary with a completely different man. She hesitated, then asked, "Can you change back?"

"Do you want me to?" he asked after a moment.

Rose nodded. "Yeah."

His face fell. "Oh."

"Can you?"

"No." He looked down at the floor, then quickly looked back up. "Do you want to leave?"

Rose gaped at him, shocked. "Do you want me to leave?"

"No!" he answered quickly. "But... your choice... if you want to go home..." He surveyed her face, seeing her still upset. He sighed and walked around the console. "Cancel Barcelona. Change to... London... the Powell Estate... ah... let's say the 24th of December." He looked up at her. "Consider it a Christmas present. There."

He stepped away from the console and tucked his hands under his arms, a little bit defensive of himself. One good thing about going back to Earth, the Emissary could help explain this all to Rose. He smiled at the thought of the Time Lady.

Rose interrupted his thoughts. "I'm going home?"

"We've got to pick up the Emissary," he answered. He paused and looked her in the eye. "Up to you, though, if you want to go home. Back to your mum... it's all waiting. Fish and chips, sausage and mash, beans on toast... no, Christmas! Turkey!" He smirked. "Although... having met your mother... nut loaf would be more appropriate." He caught a hint of a smile as Rose looked away quickly. "Was that a smile?"

"No," Rose denied.

"That was a smile..."

"No, it wasn't," she insisted.

"You smiled..." he teased.

"No, I didn't."

"Oh, come on," he said to her. "All I did was change, I didn't—" He broke off, gagging.

Rose looked back at him sharply. That didn't sound good. "What?"

"I said I didn't—" He broke off again, retching horribly. He doubled over with the force of it. When he straightened back up, his face was worried. "Uh oh."

Rose edged a bit closer to him. "Er... are you alright?" She blinked as wispy golden energy floated out of the Doctor's mouth. "What's that?"

"Oh... the change is going a bit wrong and all," he said simply before he retched again.

He hit the floor on his knees, face twisted with pain.

"Look..." Rose tried to think. "Maybe we should go back." They needed the Emissary but she didn't know how to get him to her. She blinked, a sudden thought occurring to her. "Let's go and find Captain Jack, he'll know what to do! He can help us get back to the Emissary!"

"Gah, he's busy!" The Doctor waved the suggestion off. "He's got plenty to do rebuilding the Earth!" He grinned as he caught sight of a lever. "I haven't used this one in years."

He flipped the lever and Rose nearly fell as the TARDIS shook wildly.

She gaped at him. "What're you doing?!"

"Putting on a bit of speed!" His voice and eyes were crazed. He stood fully and darted around the console, turning knobs and flipping levers. "That's it! My beautiful ship! Come on, faster! That's a girl! Faster!" He grinned crazily at Rose. "Wanna to break the time limit?!"

"Stop it!" Rose shouted, fear filling her voice.

"Ah, don't be so dull," he sneered, "let's have a bit of fun! Let's rip through that vortex!" He suddenly met her eyes, back to normal. "The regeneration's going wrong. I can't stop myself. You have to trust the Emissary." He grimaced in pain, holding his head. "Ah, my head..." Like a flip of a switch, he was back to acting insane. "Faster! Let's open those engines!"

A bell chimed loudly.

"What's that?" Rose asked.

The Doctor popped up right next to her, laughing maniacally. "We're gonna crash land!"

Her jaw dropped. "Well then, do something!"

"Too late! Out of control!" He ran around the console, giggling. "Oh, I love it! Hot dawg!"

"You're gonna kill us!"

"Hold on tight, here we go!" he warned, still laughing.

Rose quickly got a better grip on the console. The Doctor eyes met hers across the console, his excited, hers terrified. He grinned.

"Christmas Eve!"

A/N

I can't believe I actually finished it. This is the first fanfiction I've ever completed. I'm still a little in shock over it.

Anyhoops.

Huge shoutout to my best friend, @Nora West-Allen, for beta reading this, i could not have done this without her. I can't figure out how to link her profile but she's on FFN as Nora West-Allen and she's on AO3 as PSEcho. Go check her out!

The Doctor is regenerated and we are full steam ahead on season two! I will be doing a sequel, don't worry, I plan to write this series through the current season.

I'm not sure when the sequel will be up, but I will post an author's note when it is up. Please don't hesitate to comment, i love hearing what you guys think.

Thank you all so much.