I wonder how hard it is to make a fake USB printer.
Like, a printer that takes any printout and goes "yep, that printed just fine" but nothing ever comes out anywhere

@foone I did that by accident in 2003 on Windows 2000.
I wrote a printer driver that was a virtualized printer, saving the EMF stream. It automatically selected the nearest one based on the room location and streamed it there. Sometimes it didn't go anywhere.

My biggest surprise was to reuse this knowledge in 2007 to implement printing in Chrome, given the renderer didn't have direct access to the printer. Heck I got a patent for that.