By Isabella Biedenharn
April 22, 2015 at 12:00 PM EDT

Josh Lieb, former executive producer of The Daily Show and author of the New York Times bestseller I Am a Genius of Unspeakable Evil and I Want to Be Your Class President, is back with another deliciously clever book. This time, he’s putting a rodent-y twist on the classic Arthurian legend of Excalibur with Ratscalibur, the story of an 11-year-old boy named Joey who gets bitten by an elderly rat, then turns into one himself. It’s a tale full of adventurous knights, suspenseful swordfights and powerful magic (well, the rats have “ragic”).

But don’t just take our word for it. In this exclusive video, Lieb’s pal Jon Stewart waxes poetic about the world of Ratscalibur—when he’s not craving brains. That’s right, in case you weren’t aware, Stewart is a zombie. “That’s why he always brings the world’s greatest intellectuals on the show,” Lieb explains. “He hungers for their brains.” Check out our Q&A with Lieb, who is currently producer and showrunner of The Tonight Show Starring Jimmy Fallon, after the clip.

ENTERTAINMENT WEEKLY: What inspired you to write Ratscalibur?

I might have come up with a really dumb pun—”The spork in the scone”—first. That inspired the whole thing, like how a pearl is born when a grain of sand gets inside a clam. I’ve always been fascinated by Arthurian legend, and also the basic story of the kid who’s a loser and who becomes a hero, and that heroism has been inside him or her the whole time. I don’t think it’s just my favorite story, I think it’s humanity’s favorite story.

Are there any other legends you want to rat-ify?

Oooh, I want to continue rat-ifying the world of knights and derring-do, but specifically, I haven’t even touched on Morgan le Fay or Mordred or the Holy Grail legend. There are so many cool parallels we could pull off in the rat world that could be really fun for kids. 

You’d be giving them a window to the old legends, too.

Maybe so. Maybe five years later when they’re reading the real deal, they’ll go, “Oh, that’s what Lieb was ripping off!”

How is writing humor for kids different from writing humor for grown-ups?

It’s pretty much the same thing: It’s the same car, you’re just driving in a different lane. You take out a lot of the dirty jokes, or some of the crasser things an adult audience might enjoy. But humor is humor, whether it’s for a baby or a 99-year-old. There’s a very small window of stuff that isn’t funny across all age groups. It’s just keeping that audience in mind, making sure you’re not putting anything in there that you wouldn’t want your kids to read.

What were your favorite books as an 11-year-old?

Well, I loved Daniel Pinkwater. His book The Last Guru was really formative for me at that time. I was also big into these old fantasy books, so I was reading a lot of E. Nesbit and Edward Eager, books about kids going on adventures and having magic. That was right before I got heavy into science fiction. I liked the Bagthorpe Saga by Helen Cresswell. Those were big favorites of mine.