After almost 20 years Bill Watterson has officially drawn another comic strip. Pearls Before Swine artist Stephan Pastis was in the right place and the right time (and also had just published this strip) and the two collaborated briefly.
Stephan Pastis's wordpress website describes the encounter.
The comic strips:
(Score: 3, Informative) by Anonymous Coward on Wednesday June 11 2014, @06:08PM
The best strip was the one where Libby leaves. That is the one that initially clued me in to something else going on as the ending was a little too familiar. http://www.gocomics.com/pearlsbeforeswine/2014/06/07 [gocomics.com]