The Simpsons' influence is felt far and wide in the pop culture universe. After 18 seasons, everyone knows Homer, Marge and their kids. Unless noted otherwise, ™ and © 2007 Twentieth Century Fox Film Corp. All rights reserved.

Good ol' Homer Simpson. Due to circumstances too convoluted to explain quickly, this week he's driving the neighborhood ice-cream truck. Before selling his wares to the waiting children he presses a big red dashboard button labeled "Disclaimer" and a message plays: "Products contain neither ice nor cream; may contain trace elements of Mexican cheese. Do not consume."

Two commercial breaks later, a Pepsi-Cola commercial airs:
Announcer: If we say 'when you rub a Diet Pepsi you get three wishes,' we have to run a disclaimer. [In a disclaimer voice:] Diet Pepsi is not a genie.

The outrageous disclaimer, completely negating what was said moments earlier is one of the dozens of recurring gags invented and exploited by The Simpsons with pitch-perfect precision. (When Krusty the Clown enthusiastically guarantees the flawlessness of one of his products, an announcer quickly adds, "not a guarantee.") Pepsi got the joke -- and stole it as well.

The Simpsons' influence is felt far and wide in the pop culture universe. After 18 seasons, it's no surprise that everyone knows Homer, Marge, their kids and Springfieldians (almost literally) innumerable. If Homer's adventures were taking place in real time, baby Maggie would be in college by now. However, as fictional cartoon characters Homer and company are spared the physical ravages of time -- and creatively, they seem to be holding up pretty well too. As of this writing the season-ending episode 400 is just a few days off (May 20, 2007, two episodes in a one-hour block 8-9:00 pm on FOX), a theatrical feature -- the only 2D one of 2007 -- is due out later this summer, and a 19th season is gearing up for the fall.

How does a show like The Simpsons stay crazy after all these years? How does it avoid taking a flying leap over that shark tank? (There are those who say it's already short a toe or two.) And what do others in the cartoon biz feel about the show that forever demolished the expression 'adult cartoon' as an oxymoron?

Outside of Matt Groening, James L. Brooks and Sam Simon, supervising director Mark Kirkland perhaps knows the inner workings of The Simpsons best.

Mark Kirkland
Mark Kirkland has been part of The Simpsons since its second season. The director of 59 episodes, Kirkland has moved up to supervising director, overseeing the show's 10 or so helmers while still taking on the occasional episode himself. If anyone (outside of creator Matt Groening, James L. Brooks and Sam Simon, the show's original developers) knows how the Simpson family keeps going and going, it's him…

Our show is parody of what we see in life. Life keeps changing and moving on. There's always new ideas for us to parody. We have a fabulous team of 25 writers. What I've seen over years is when a writer feels like he's done his thing, he moves on and creates a seat for a new one who's filled with new ideas. Sometimes we catch ourselves however. We have lots of story meetings, animatics and someone will say "didn't we do that?" and point out it was done five or 10 years ago.

We don't use a focus group -- we're our own focus group. We read what the [online] fans say, but fans aren't writing the shows. All the people working on the shows are also fans. We kind of create the show for ourselves.

FOX keeps hands off because we're kind of a grandfathered-in contract, because of the way the show was set up. James L. Brooks had the ability in that day. If the term is "600-pound gorilla," he's a thousand-pound gorilla, the strongest man in the business.

The characters have evolved, they have changed. The early Homers were different from where Homer is now. In the early years of the show I recall attending a lot of meetings where Matt Groening didn't want Homer as stupid.

Basically, if something's getting a laugh and is entertaining, we kind of keep things in that direction. Matt is still involved, James L. Brooks has been watching. About one or two years before the feature he started checking in with the episodes more. He had been really busy directing live action, but he started paying more attention, giving notes to the writers like, 'I want more stories that focus on the family.' James and Matt helped pull it back in line, they're the creators. They don't micromanage, but they do kind of guide where they want it to go.