When I was a kid, Commander Keen was my favourite game. And it was awesome!
Unfortunately, I only had one game in the series, and my parents weren't... keen... to send their credit card details over the phone to a company overseas. This was well before Internet, mind you. So I couldn't get the rest of the games, even though I really wanted them.
Instead, I started designing my own games and stories on a magnadoodle. That's how I developed my love of storytelling.
Then, when I was in year five, my teacher read to me the Chinese creation myth. That triggered a spark in my mind, which over the years transformed into an invented world, with its own mythology, languages, and history.