The TARDIS, just after the events of The Christmas Invasion

The Doctor grinned as he danced around the controls, pulling levers and pressing buttons. Rose Tyler watched, silently laughing.

"So, where are we going today?" she asked.

"How about Adipose One?" he suggested. "It's a nice place."

"Fine by me!" Rose responded.

"All right, Allon-sy!" he said, pulling another lever. Suddenly, the TARDIS started shaking.

"Is that good or bad?" Rose said nervously. The Doctor frowned, peering at the screen before being thrown backwards.

"I dunno what it's doing!" said the Doctor, putting on his glasses and grabbing the screen again. Then the TARDIS threw them more violently and both blacked out.

Rose slowly drifted into consciousness. When she finally pried her eyes open, the Doctor was on the floor nearby. But something else seemed off-his suit seemed baggy on him. What's more, her own clothes were hanging off of her! She looked in a mirror, and confirmed the worst-she had woken up in her fifteen-year-old body. She went back to her room on the TARDIS and started digging through a dresser for something that fit her when she heard the Doctor.

"Rose? Are you allright?" he asked. He sounded a lot younger than he did before. "What's wrong with my voice?"

Rose poked her head out of her bedroom. "Something strange just happened, Doctor!" She sounded younger herself.

He finally noticed his baggy suit. "Hwhat?" he managed, and ran towards the bathroom to look at himself in a mirror. Rose resumed her search, hearing more "Hwhat?"s from the Doctor, and found a small dress that had shrunk in the wash. She put it on. Well, it could be worse, she thought, before walking back outside.

The Doctor walked out of the bathroom, looking puzzled. "I think we just fell through some sort of temporal rift," he said. "But how did this happen?" He then walked off to the TARDIS wardrobe. Rose went back to the console room and looked at the screen.

"Doctor? It says we're on Earth!"