"This is the story of the most extraordinary child who ever stuck his tongue out at the Prime Minister. His name was Nicobobinus. He lived a long time ago, in a city called Venice, and he could do anything.I recently came across a copy of Nicobobinus in a second-hand book shop and snatched it up. It was a vague memory from my childhood, which I probably read when I was about 8 or 9 years old. But something of it had always stuck with me - nothing much more than an evocative mood, really, most likely thanks to Michael Foreman's wonderful illustrations (which were always a winning combination with Terry Jones - see this old post for more on this), but one powerful enough to have never quite been forgotten.
"Of course, not everyone knew he could do anything. In fact, only his best friend, Rosie, knew, and nobody took any notice of anything Rosie said, because she was always having wild ideas anyway.
"One day, for example, Rosie said to Nicobobinus, 'Let's pull up every weed on your doorstep.'
"'Let's not,' said Nicobobinus (which is what Rosie thought he would say).
"'In that case,' replied Rosie, 'Let's discover the Land of Dragons!'
"'Don't be daft,' said Nicobobinus, 'How can we do that?'
"'Because you can do anything,' said Rosie."
The concept of somebody who can "do anything" deliberately going to discover a place which does not exist, and in doing so thereby calling it into existence, is fairy tale logic at its finest. But something like this also happens a lot in games, whether by design or otherwise. No, one doesn't tend to begin a campaign with the PCs announcing they want to discover a place one of them has plucked from thin air. (Although you certainly could.) But one does tend as the DM to create people, places and things on the fly as the players ask questions either in- or out-of-character. Hence:
Player: "I ask NPC X where he's from."
DM [who has just invented NPC X because the situation has called for it, perhaps because the players are in a tavern and asked something like "Who is sitting next to us?" and has given his background no thought]: "Er, he says he's from the land behind the mountain."
Player: "Ooh, I wonder what that's like..."
And suddenly there's a land behind the mountain where there was none before. One which the PCs might well end up visiting and which the DM is going to have to detail when all it was originally was a phrase which popped into his head in the heat of the moment.
I intend to call this form of knock-on creation the Nicobobinus Gambit from now on. The DM in the mini-scenario I just described deployed the Nicobobinus Gambit as an emergency measure. (It was an Emergency Nicobobinus Gambit, if you will.) But it is entirely possible to use the Gambit in a pre-planned way. The most obvious example I can think of is that DM beginning his campaign by sitting down the players and asking them, "So, where is your PC from? Make something up."