Story highlights Bill Watterson contributed to the comic "Pearls Before Swine"

Watterson contributed three strips

The series of strips ran nationally this week

Almost 20 years ago, Bill Watterson walked away from "Calvin & Hobbes" -- the wildly popular comic strip he created and illustrated from 1985 until 1995.

Fans of the mischievous 6-year-old boy and his sardonic stuffed tiger have been left wanting more ever since.

For the time being, they can at least take comfort in some cameo work released this week.

Stephan Pastis writes "Pearls Before Swine," which chronicles the lives of its main characters -- Pig, Rat, Zebra and Goat, and the dreaded Crocs. He's also a big Watterson fan. Last spring he attempted to reach the notoriously reclusive comics legend via e-mail, to no avail.

Undeterred, Pastis included a "Calvin & Hobbes" reference in his next strip.

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In it, Pastis approaches a woman at a bar and uses his profession to impress a female patron. When the woman asks which strip he draws, Pastis says "Ever heard of 'Calvin and Hobbes?'" The two end up in bed, a thought bubble above Pastis' head says: "That was wrong."

Shortly after that, much to Pastis' surprise, Watterson replied. "Just getting an email from Bill Watterson is one of the most mind-blowing, surreal experiences I have ever had. Bill Watterson really exists? And he sends email? And he's communicating with me?" Pastis wrote on his blog

Not only was Pastis in communication with him -- Watterson wanted to collaborate. The two decided that Watterson would contribute panels to three "Pearls" cartoons.

The series of strips ran nationally this week with the premise that a small girl named 'Libby' (or 'Lib') would stand in for Pastis.

According to Pastis' blog , 'Lib' is "a precocious second grader who thought my art was crap" and is really a cheeky inside joke. (Hint: 'Lib' is almost 'Bill' spelled backward).

In the first of the three strips, 'Lib' draws two crocodiles eating Pastis.

The second strip is more reminiscent of Watterson's "Calvin & Hobbes" days and features a "Martian robot attack" that could be seen as nod to Calvin's alter ego Spaceman Spiff.

The third ends with Pastis asking Lib if she'll draw his comic forever. "Nah. The art form's dying," she responds.

According to Pastis, having the legendary Watterson draw his strip is like working with "the Bigfoot of cartooning" -- rare, and the highlight of his career.

Millions of fans feel exactly the same way. Many took to Twitter guessing correctly that Watterson was the guest comic.