Hello, my name is Isobel. I am tall, with grey-blue eyes, bushy raven black hair and green skin. My dress is black, shot through with all colours. At least, it is now. I can look like anything I want. I like basing myself on book or film characters. At the moment I'm Elphaba from Wicked. ANYHOW.

This is the story of how my secret appearance was revealed. As per usual, it involved the Doctor.

He was obviously intrigued when he first met me as he had just witnessed a transformation. I'd turned from a slightly alternative representation of Sadie Kane (I had wings) into my current form of elphie.

At first, I panicked and nearly sliced him in half with a beam of light (I can give myself any magic power I want), before I noticed the police box in the corner. I nearly fainted, staying conscious but still falling over.

He picked me up and took me into the TARDIS. The interior was all crazily slanted walls and angles, and coated in blue lights. The Doctor set me down on a bed. I had a headache and the room smelled of lemons or... Teleports?! He appeared round a corner. How did he do that? I didn't have time to mull it over as at that moment something about the size of a fruit bat came hurtling round the corner and smacked straight into the Doctor's head. Doctor and thing fell in opposite directions, like some grisly stunt from a film.

I manoeuvred the doctor onto my bed and picked the thing up. It was warm and smooth - about the size of a bul... It was a bullet! A bullet with wings, coated in blue lights, like the Tardis itself. The doctor whispered behind me "thing. Here. Now." I gave it to him and he stroked it lovingly. The lights on it went out. "What's got you all worked up?"

And then we said in unison "Tardis defensive mechanism?!"

Then the doctor said "it seems to be allergic to something in here"

"Let's see what this does" I imagined my normal form: a bony, mid-height girl with wide grey-blue eyes and thick, wavy strawberry-blonde hair so dark it is almost brown. The lights on the thing turned green and then it spoke! It said, in a thin, tinny squeak, "Target Unarmed 1, Repeat, Target Unarmed 1"

I asked the doctor what it meant. He said "Long story short, it thought you were hostile, and now it knows you aren't. It detected a glamour. Your imagination. The Imagination that can affect the real world. Anyway, I've detected a time paradox in the Andromeda galaxy"

"Let's go!"

Yes!