He did do a guest week on Pearls Before Swine post-retirement. https://slate.com/culture/2014/06/bill-watterson-does-pearls-before-swine-the-calvin-and-hobbes-c

He did do a guest week on Pearls Before Swine post-retirement. https://slate.com/culture/2014/06/bill-watterson-does-pearls-before-swine-the-calvin-and-hobbes-creator-emerged-from-retirement-to-work-with-stephan-pastis.html https://slate.com/culture/2014/06/bill-watterson-does-pearls...