While Zen Pencils is using older written quotes (it's the theme of the comic), the recent comics documentary 'Stripped' has the honor of the first audio interview with Bill Watterson. He initially declined, but after their interactions with dozens of other cartoonists, word got to Bill that they were "the real deal" and passionate about what they were doing. Rather inspiring.
Watterson is the most notoriously reclusive artist in his field - if somebody got an interview with him, that's a feat.