"I lost my shoe!" said the Doctor.
"Your shoe?" asked Donna Noble.
"Yes. My shoe." The Doctor hopped on one foot, waving his bare foot at Donna.
"I don't want to look at your foot," said Donna, "How did you lose your shoe?"
"I put it somewhere, and I forgot where. How do you lose your shoes?"
"I don't!"
"Well, I can't find it."
"Why don't you wear your other shoes?"
"I don't want to!"
The Doctor hopped around the TARDIS, pouting. Donna sighed.
"Where would you put your shoe?"
"Where it belongs!"
"Did you look there?"
"Of course I did! The other one was there!" Donna sighed.
"Spaceman, losing your shoe."
"My foot's cold," said the Doctor.
"Well, if you won't wear different shoes, why won't you try a sock?"
"Don't like them."
"Of course."
Two Days Later
The still one-shoed Doctor stepped out into Cardiff, shoved by Donna Noble.
"But now I'll have one and a half pairs of red shoes, and that's just daft."
"You are not going around the universe with one shoe on!"
"Oh, fine..."
"Hello, sweetie."
River Song stood on a street corner, holding up the Doctor's missing shoe.
"My shoe!" said the Doctor, hopping across the street.
"How'd you get his shoe?" asked Donna. River put a finger to her lips as the Doctor put his shoe back on.
"What'd you need my shoe for, anyway?"
"Spoilers."