My turn!
This would be set around "The Idiot's Lantern," as I'm an absolute sucker for scooters. This seemed a whole lot cuter in my head, but anyways...
The Doctor had flown out of the TARDIS on a vintage blue Vespa. Rose joined him, and they rode off together down the street.
A miniature version of the Doctor peeked out at the bottom of the TARDIS door, watching them go. He raised an eyebrow, and a mischeivious grin spread across his little round face. With a squeak, he disappeared back inside.
*afterwards*
“Well, that was an odd one, wasn’t it? A creepy face sucking people inside their telly.” Rose was leaning against a wall in the control room.
“Oh, you think that was wierd? You should see the...” The Doctor’s voice trailed off. “Do you hear that?”
“Hear what?”
The Doctor scratched the back of his head. “I’m not sure. If I had to guess, it almost sounds like a mosquito, only mechanical.” For some reason, this seemed to concern him. Rose just shrugged.
“It’s probably just the chibis up to something again.”
The Doctor rolled his eyes. “Oh, well that’s just fantastic.” He couldn’t have added anymore sarcasm if he’d tried.
Ten seconds later, the sound grew slightly louder, and the tiny chibi Time Lord rode into the control room on a miniature scooter. When he got to the other side of the room, chibi Rose was there waiting for him, in a familiar pink dress. She hopped on the back of the scooter, chibi Doctor gave a thumbs up, slicked back his hair, and took off again. They made three loops around the console, and sped out of the room giggling. The larger Time Lord looked absolutely horrified.
There was silence for a moment, and not being able to hold it any longer, Rose doubled over in laughter. A disgusted look settled over the Doctor’s face. He let out a big sigh, and walked out of the room, looking as tired as if he’d just been defeated by a swarm of Daleks.