Bill Watterson, creator of the fabled and much-missed “Calvin and Hobbes” comic strip, got back in the game for a while this past week as a guest artist for the Stephan Pastis strip “Pearls Before Swine.”

The famously reclusive Watterson, who sent Calvin and his stuffed tiger sledding into history in 1995, collaborated with Pastis in part for fun and in part to help raise money for Parkinson’s research, according to Michael Cavna of The Washington Post.

Pastis did the writing and some of the drawing, turning Watterson loose in the middle panels. And both apparently had a wonderful time.

“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 planned to! It was a lot of fun.” Watterson told Cavna.

As for Pastis, he said: “It’s just massive … the biggest thing I’ve ever been a part of.”