Back in 1983 I moved into my first share house, with my high school friend Brad and my university friend Leigh Southall. It was an old 1940s house with cracking plaster, and was pretty much the direct inspiration for my first Cthulhu scenario "The Crack'd and Crook'd Manse".
As you can imagine it was quite a gaming household; we played a ton of RuneQuest and Call of Cthulhu.
Leigh used to sit in his chair, elegantly dressed in white shirt and vest, drink endless cups of coffee and smoke endless cigarettes, and fill sketchbooks with line art. He drew a lot of RuneQuest characters which we used for local tournament modules and the fanzine that Penny edited for a stint (The Devil's Advocate); some of his art also made its way into Tales of the Reaching Moon.
Then one day he had a crossover moment between RQ and CoC, and started sketching duck investigators. The Quack of Cthulhu was born.