This is a response to Jessa L'Rynn's July Challenge 1. There is much crack ensconced in here.
Disclaimer: I own nothing except maybe, MAYBE this theory.
WARNING: Not a single character has been behaving themselves recently. Originally this was going to be Rose. She sounded more like Martha. I have no idea who she is or even which Doctor I'm playing with here. I am about to watch RotC/AoS and very possibly TIL to stop myself from having Rose and Martha act pretty much the same.
The Time Lord in question jumped a little at his companion's intrusion and silently thanked whoever might have been listening that he hadn't been under the console at the time.
"I've just been wondering..."
The Doctor paled a little bit. Companions saying they were wondering about something, particularly in that innocent tone of voice, was bad. It usually meant he had done something wrong. What had he been doing that might be construed as "wrong"? He flitted through his mind for a moment.
All right, so maybe taking her to that one planet might not have been the best option, but how was he to know that the great big mauve thing was going to blow up as soon as they got within ten feet of it?
"Why does the TARDIS make that noise?"
She rolled her eyes just a little bit. "When that thing goes up and down?" she prompted.
He opened his mouth to correct her on what "that thing" was, but caught her warning look and just nodded.
"You know that roaring sound she makes every time she does that?" she prompted again.
The Doctor nodded again, getting a little irritated.
"Why does she do that?"
He was a little relieved to know that the answer was simple.
Hey, it's a valid theory... maybe... Okay, so it isn't. But do I care? Nope.