"We just recorded the Ricky Gervais episode," he lilts in the thin high vowels of his Detroit upbringing. "He really wanted to do something where we satirised Wife Swap. So there's this story where he sends his wife to the Simpson family in exchange for Marge, who he woos with flowers and a song. It's a very funny episode."
Jean, who is big and bluff-looking, resembling an outgrown 44-year-old college boy in a polo shirt and slacks, giggles at the thought. "Ricky was over to collect his Golden Globes for The Office. There are so many of our writers who are fans of his that we thought we'd throw a lunch for him. And he mentioned that he would be interested in writing an episode with us. Before we knew it, it was worldwide news."
Gervais is one of the long line of celebrities who have jumped at the chance to be immortalised on the world's most famous animated series - Thomas Pynchon, Stephen Hawking and Tony Blair are among those who have appeared as "themselves". And it is always Jean who flies out from Los Angeles, where he lives with his wife, to meet the prospective stars. "They're all fans - that's important," says Jean. "So is Ricky. That's why he wanted to do it."
So are there any other fans out there whom Jean would like to include in future episodes? "I was slightly taken aback that the Archbishop of Canterbury was such a huge fan. Maybe we'll have to get him on. But I'd be really surprised if we could make a fan of the new Pope."
It could all have been so different for Jean, who has been a writer for the show since its inception in 1989. "They were looking for writers to transform the Tracy Ullman Show shorts into half-hour episodes, and I was one of the first hired. A lot of my writer friends didn't want it because it was a cartoon, but I looked at the names - James Brooks, Sam Simon, Matt Groening - and I knew that at least it would be a good show. The fact that it was animated would at least make it stand out. So I took the job."
Jean, who had been working with Garry Shandling (of Larry Sanders fame), and previously on National Lampoon Magazine, admits it was a win-win situation. "It wasn't that much of a risk. We were taking four months off between Garry Shandling seasons, so we had time. The Simpsons was offering two-days-a-week jobs on the first 13 episodes. It was a case of getting in on the ground floor of something that was more successful than my wildest dreams."
Back in 1989, there were five writers. Now there are 20 - "absolutely the best writers in town". With this small army of brainpower, it is a military operation to take a concept from first giggle to finished product. "Generally, one or two of the writers will pitch a show to me. But I'm very particular about which ideas go through to being a script. Once the idea is okayed, it is turned into a first draft by the original writer. Then the rest of the staff get their hands on it, and rewrite it four or five times before the cast even sees it.
"All the while, we're tweaking it and making small gag changes, while the cast is adding ad libs. The show is then sent to the animators, who do a rough version called an animatic. We then rewrite. And once we've done that, we send the whole thing to Korea, where they do the final colour animation. Between first idea and show is about a year."
Can that backfire horribly? "Oh, sure," Jean says. "We wrote an episode which included the Soviet Union. By the time it was about to air, the Soviet Union had broken up and we had to change the whole thing. But we're not doing shows with material you can't understand three or four weeks later. We're shooting shows with wider trends. So we can make jokes about how hard it is to buy prescription drugs in the US, or gay marriage, or assisted suicide. They're all going to be in the ether in a year's time."
It's hard to imagine the con-servative Fox network loving the assisted suicide material. How does that relationship work? "We've never had any trouble from Fox," Jean says diplomatically. Not even the constant ribbing of Fox's broadcasting standards (Bart famously says that "Fox'll show anything!")? "No, nothing. They're good sports."
He continues: "This show wouldn't exist without Fox. When we started out there were only three networks in the US. Someone had to gamble $13m on The Simpsons, and Fox were willing to try something new and very risky. They let the show have the freedom it wouldn't have had on any other network.
"But, then again, I figure that the show is making money every time it airs in the US. Throw in overseas sales, syndication, DVDs, and The Simpsons is still a huge bargain for Fox. And I realise that to keep the show a commercial success, people have got to keep loving it artistically."
So what does this guardian of The Simpsons' heritage think of the view that the show has not been the same since the "golden years" of seasons three to five? "Well, I remember people saying the show had gone downhill since seasons one and two," he says. "It's just human nature. There are very few cultural things that people think are better now than they were. I don't perceive any drop in quality."
Something did happen between the first two seasons and the next three, though - a shift from a Bart-centred show to a Homeric universe. "Yeah, people say that, but it was totally unconscious. We just started doing more Homer-based episodes. Bart was enormously popular, and still is, but when we were pitching ideas, we found it easier to think of stories for Homer than for Bart. That's maybe because a 10-year-old boy doesn't have quite as rich a life as a grown man. Plus, the writers have grown closer in age to Homer. Right now, we're moving into Abe territory. There do seem to be more Abe episodes than normal coming up."
Jean seems keen to dismiss suggestions of greater patterns behind The Simpsons. The show is, he seems to suggest, just funny. I wonder what he thinks of the wealth of philosophical and theological Simpsons literature. "Yeah, you can do a course on it at Berkeley," he laughs. "I guess it's OK. The only caveat I would have is that there is no common sensibility or religious belief that the show has, because it's the product of a number of people.
"If there was one sensibility that the show espouses, it might be this thing that there are these large impersonal forces in the world who are out to destroy the little guy. But the show doesn't have a position, say, on gay marriage. We let the viewer decide. I have heard people say that The Simpsons is an easier way of getting students into philosophy than reading Schopenhauer and Nietzsche, but whether that makes us a good or a bad thing, I don't know."
Do The Simpsons' high standards make Jean anxious? "It's daunting. The show is so beloved. I don't want to be the guy who presides over the show when it loses that. It's the most daunting thing in my life." Now I understand how the funny guy on the sofa got so serious.
New episodes of 'The Simpsons' air at 7pm weekdays and 6pm weekends on Sky 1
Al's greatest hits
* Marge Takes The Kids to See Their Grandfather
Marge: Dirty words. Drinks. Adult boardgames. I'm so glad I sent the kids to Grandpa's to protect their innocent minds.
Grandpa: (showing Bart and Lisa a series of pictures in a photo album) And here are some more Germans we killed. That flamethrower really sausaged their waffles.
Bart/Lisa: Ewwww! Gross!
Lisa: Grandpa, how do you sleep at night?!?
Grandpa: They drug us.
* Homer Battles With His Inner Capitalist
Homer: Aw, $20! I wanted a peanut!
Homer's Brain: $20 can buy many peanuts!
Homer: Explain how!
Homer's Brain: Money can be exchanged for goods and services!
* Barney Decides To Hop on the Wagon
Barney: Hello, my name is Barney Gumble, and I'm an alcoholic.
Lisa: Mr Gumble, this is a girl scouts meeting.
Barney: Is it, or is it you girls can't admit that you have a problem?
* Marge Rumbles Homer Cheating at College
Marge: An A+, how did you do it?
Homer: Oh let's just say I had help from a little magic box!
Marge: You changed your grade with a computer?
* Homer and Bart Sweet-Talk the Girls
Homer: Is that Lisa? Oooo, I gotta call heaven. There's an angel missing!
Bart: And who's your little school friend? Wait a minute... That's Mom!
Marge: I know two fellas who will get a special dinner tonight!
(Bart and Homer give each other a high five)
Bart: Dad, do you know anything else about women?
Homer: Nope, that's it.
* Chief Wiggum Lays Down the Law
Wiggum: All right, smart guy, where's the fire?
Homer: Over there.
(Homer points to the police station, which is on fire)
Wiggum: Okay, you just bought yourself a 317: pointing out police stupidity. Oh wait, is that a 314?
No, 314 is a dog, uh, in, no, is that a 315? Eh, you're in trouble, pal.