Archancellor Ridcully slowly walked around the blue box. It looked safe enough, despite the weird noise as it appeared. -- Anon Guest
And then someone who looked almost exactly like that fellow from the post office popped out from the door. "Oh hallo," he said. "I seem to be very much lost. You see, I was on my way to Barcelona, and..." He trailed off. "Have I been here before?"
Archancellor Ridcully had a train of thought that couldn't be shifted from its rails. "I'm not buyin' anything off of yer no matter how shiny it is," he said on automatic.
The man in the smart suit and plimsols stepped out. "Doesn't sound like me," he sounded convincingly confused. Waved around something that buzzed as it lit up. "Hm. Heavy thaumic fields... I'm guessing you get semi-regular incursions of parallel realities full of eldritch abominations? Hi. I'm the Doctor."