Tah-dah! Look at that bright, shiny light bulb, right above my head!
That, my friends, is an idea. They are very rare, the good ones, at least, so treat it carefully or you might scratch the glass.
Though they don’t always show up in the form of a light bulb (in fact, I’ve never had that happen), ideas come. Yeah, try telling that to the author with five deadlines looming above their head while they’re staring at a blank screen.