Some artists, such as Jack Kirby, need no plot at all. I mean I’ll just say to Jack, “Let’s let the next villain be Dr. Doom” ... or I may not even say that. He may tell me. And then he goes home and does it. He’s so good at plots, I’m sure he’s a thousand times better than I. He just makes up the plots for these stories. All I do is a little editing ... I may tell him that he’s gone too far in one direction or another. Of course, occasionally I’ll give him a plot, but we’re practically both the writers on the things.
STAN LEE, Castle of Frankenstein, no. 12, 1968
He definitely gave some credit to Kirby, but he claimed to have created/invented several characters when they were joint creations. On individual issues, they shared the credit with both their names equal size.