Doesn't need much introduction; Rose decides to play a game with the Ninth Doctor. Covers from after Nine and Rose met to post-Doomsday.
Disclaimer: Doctor Who and all characters mentioned herein belong to the BBC.
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"Hey Doctor, d'ya like to play a game?"
Rose's grin was infectious and he gave easily. With a matching grin on his face, the Doctor replied, "Sure."
She patted the seat next to her excitedly. After he sat, she leaned in and said,
"Knock-knock!"
Off his look, she whispered, "You say 'Who's there.'"
"Oh."
"Knock-knock."
"Who's there?"
"Doctor."
"What?"
"No, who."
"Me?"
"No, who. You're supposed to say who."
"Oh. …Why?"
"Who!"
"I was asking why!"
"Why what?"
"Why are you saying you're me and I have to pretend I don't know who you are?"
"It's a joke; you just go along with it."
"But--"
"Never mind," Rose sighed. The Doctor just looked nonplussed.