Earlier today, former-San Francisco lawyer/now-syndicated cartoonist Stephan Pastis, revealed that legendary "Calvin and Hobbes" creator had contributed artwork to Pastis' "Pearls Before Swine" comic strip this week. Apparently Pastis had struck up an email correspondence with the reclusive Watterson, and Watterson had an idea for a strip. Pastis replied, "Dear Bill, I will do whatever you want, including setting my hair on fire.”

Pastis writes, "The idea I proposed was that instead of having me get hit on the head, I would pretend that Pearls was being drawn by a precocious second grader who thought my art was crap. I named her 'Libby,' which I then shorted to 'Lib.' (Hint, hint: It’s almost 'Bill' backwards.)"

You can read the whole series here (click the arrow to advance to the next day's comic).

The Washington Post spoke to Watterson (!!) about the collaboration:

So what, exactly, lured Watterson back to the page for the first time since ending his immensely popular boy-and-tiger comic in December of 1995?

“Several years ago, when Stephan did one of his strips that mocked his own drawing ability and mentioned my strip in comparison, I thought it might be funny for me to ghost ‘Pearls’ sometime, just to flip it all on its head,” the goateed Watterson tells me, offering a clear indication that he still follows the funnies. “It was just a silly idea, and I didn’t know Stephan, so I never pursued it, and years went by.”

Then, earlier this year, Pastis contacted Watterson again, and Watterson thought they could work together and help promote and raise money for Team Cul de Sac, "a charity co-founded by Sparks and cartoonist-illustrator Richard Thompson that raises funds to fight Parkinson’s disease, in coordination with the Michael J. Fox Foundation."

Watterson also told the Post, "I think we both got some surprises. I didn’t know what he was going to write, and he didn’t know how I was going to draw it." And Pastis did make some suggestions, "It was like editing the pope. Like telling Michelangelo: ‘David’s hands are too big.’ "

Watterston added, “I had expected to just mess around with his characters while they did their usual things, but Stephan kept setting up these situations that required more challenging drawings ... so I had to work a lot harder than I had planned to! It was a lot of fun."

Pastis has more details about how they worked together on his website, " I found out that Bill Watterson is not comfortable with scanners or Photoshop or large email attachments. In fact, by the end of the process, I was left with the distinct impression that he works in a log cabin lit by whale oil and hands his finished artwork to a man on a pony."