They come from my brain, here's the process:

• Let the hampsters from their cage and feed them breakfast
• Put them onto the hampsters wheel in my head and get them running
• Engage the gears, pulleys and cogs that makes my brain work
• Start thinking up ideas
• Write them down

It's been 202 weeks without missing one so far, pretty good and, the same hampsters too!

Ok, not really, I work then so hard they only last a month or so before escaping to find greener pastures and less physically taxing work. (I don't pay them much either )