You may or may not be acquainted with Poison Pen Letter, a mostly-fizzled collaborative comic I was doing with Jon Cairns. It was 100% improvised and unscripted, with each of us taking turns drawing a page to play off the other and advance its indeterminate story. (Jon drew a page, I drew the second, he drew the third, and so on.)
After years, I drew another page.
Read the previous pages here.