"The Simpsons already did it."

That's not a valid argument to make anymore, South Park, not when The Simpsons is still doing it (in this case, "doing it" equals "making all-new original episodes") after 25 years on the air. That's right: Later this month, the longest-running American primetime scripted series extends its run for a milestone 25th season.

"It's an astounding number to all of us," executive producer Al Jean said during a conference call with the press. Jean, who was part of the original writing staff on The Simpsons, has served as showrunner since 2001. "What it means is, whatever happens, if anything goes wrong, it's your fault," he joked. But based on his comments, Jean and his writing staff don't have much to worry about in the "doing it wrong" department.

"I think this upcoming season is one of our best ever," he said. "There are some extremely ambitious episodes toward the end of the year that are unlike anything we've done before."

Season 25 premieres Sunday with an episode called "Homerland." Fans of a certain Showtime drama can draw their conclusions about what the episode entails.

"It was an idea pitched by one of our writers, Stephanie Gillis," Jean said. "The fact that Homer works at a nuclear power plant lends itself to him being somebody who could be turned by nefarious forces to do something terrible. And there's the fact that you just add an 'r' to Homeland and you get 'Homerland.'"

Another happy coincidence: "Homerland" airs the same night Homeland premieres its third season. The timing was a "complete accident," Jean said, but the premise of the episode was anything but.

"When you have a basic, great dramatic premise — is this person a traitor or a hero? — that's something you can turn into comedy very easily," he said. "Particularly the scenes where his daughter is discovering what he's doing. We thought that would work very well with Lisa and Homer."

There's even more drama in store for Homer later in the season, when the Simpsons patriarch finds himself trapped in an elevator, forced to help a woman (played by Mad Men star Elisabeth Moss) give birth.

"She's grateful, she doesn't have a husband, so she names the baby Homer Junior," Jean revealed. "Homer bonds with this baby better than with his own children — and Marge gets very mad."

But it's not just the nuclear family getting in on the action this season. One future episode involves Comic Book Guy getting married, with none other than Stan Lee presiding over the ceremony. And on a darker note, Jean teased that an established Simpsons character is on their way to the great beyond.

"We're working on a script where a character will pass away," he confirmed. "I'll give a clue: The actor who plays the character won an Emmy for playing that character. I won't say who it is."

Speaking of dark themes, the opening for The Simpsons' annual Halloween tradition, the “Treehouse of Horror” episode, is in the hands of horror master Guillermo del Toro this year.

"It was amazing, what he did," Jean said of del Toro's work on the episode, airing Oct. 6. "I've met some people who like scary things, but he's the greatest expert on horror movies that I've ever encountered. There are so many references in that opening that he put in. It's really brilliant."

Much later in the season — right around finale time, in fact — The Simpsons will have a full-on crossover episode with the cast of Futurama.

"I've been here for 25 years and we had a read for [the Futurama episode] yesterday where the excitement was as high as I've ever seen," he said. "We had John DiMaggio and Billy West and Maurice LaMarche from Futurama, and we had our cast. I thought, 'This has got to be the best voice-over talent at one read that I could ever think of.' It was really great seeing Bender interact with Homer. I can't wait to see that episode."

With all eyes on the show's 25th season, there's one area of Springfield that isn't getting much attention these days: the movies. Jean said there are no active plans for a follow-up to 2007's The Simpsons Movie, even if the possibility isn't completely off the table.

"The really honest answer is, we talk about it from time to time. We say we'd like to do one," Jean said of making a second Simpsons movie. "But I will say there's a unanimous feeling that nobody wants to do a bad movie or a movie that looks like it's for the money, or anything that doesn't have the attention that the first movie got lavished on it. If we come out with one, it won't be for a while, and it will only be because everyone working on it would say, 'This is a great movie. We want to do this.'"

Perhaps that's why The Simpsons is still active after all these years: Jean and his team do what they want with the show, and very little else.

"It's a pretty small list of what we've wanted to do where we've been told 'No,' and a pretty long list of amazing things we can't believe we've been able to do," he said. "You can go to a Simpsons [theme park] in Universal, Florida. There's a play on Broadway that we didn't write, but it's inspired by an old episode. It's crazy. It's really nuts what's come about because of this show."

"Animation is the most evergreen thing there is," he added. "I'm really glad I do it."

The Simpsons begins its 25th season Sunday at 8 p.m. ET/PT on Fox.