On Strips: 1999 Ketcham Interview
I came across this public access show from Monterey County, California where they spend time with local celebrities. Including Dennis the Menace creator Hank Ketcham. It's a little shy of a half hour of Ketcham just relaying his own story to the camera, followed by a short visual tour of his studio. I don't see a formal date of the production, but Ketcham appears to date a sketch with "2-2-99" at the end of the video.