Try this on for size, hmmm?

Jack stared into the cloudy tank, trying to discern a shape among the mist, but there was none. All there was was a voice, vowing to destroy the human race. Jack took a deep breath-

-but his next sentence was cut off by a flash of light and a high-pitched buzzing, as a man materialized right in front of him, facing the 456 tank. From behind Jack could see that he was wearing a tweed jacket and a bright red fez, and was holding a mop, at which the man stared with some perplexion. Then he seemed to notice the tank.

"So," he said, in a bright, nasally voice, "just what exactly do you think you're doing here?"

"We," said the slow, deep voice, "want the children."

"Oh, of course, you want the children," the man began pacing before the glass wall. "Of course, of course, of- NO! You don't get to come take children from random planets! You've been restricted under section five-acorn-beta-two of the Shadow Proclamation from planets above a level four, and guess what," he gestured at the floor. "This is level five. SO!" Jack jumped at the sudden raise in the volume, "I suggest that you let those children from 1965 go, back exactly the way they were, lift the psychic wave from all the kids, and bugger off back to your own galaxy before I have to stop you, because make no mistake. I will."

"We…" began the 456, "do not…fear you."

"Oh, you don't, do you?" The man tossed the mop from one hand to the other. "Well, that was only your first mistake. Scan your records, go ahead. Because you're not the first to come to this planet, not by a long shot. Mm-hmm, check out all those other guys and what they wanted to do to Earth's inhabitants. Now look at the success rate. Zero percent. Zero percent. And do you know why that is?"

The man stopped pacing and held the broom still. "Because of me. Hello." His voice was still bright and cheery, but Jack shivered at the underlying menace it contained. "I'm the Doctor. Basically…run."

Jack stared at the man's back. The Doctor! There was a great trembling roar, and a column of flame shot up at the ceiling from the glass tank. The room seemed to suddenly glow much brighter. The man turned around to face Jack. He grinned.

"Hello, Captain. Nice to see you again! And Ianto Jones, I've heard so much about you. Been keeping busy, have you?"

Because this was all I could think of while I was watching Jack talk to the 456.