Being animated has helped, of course. The characters never have to age. But the show hasn't succeed merely by avoiding the horrors of a cute child star growing to a surly teen on screen.

The Simpsons was revolutionary for being the first show on TV about TV. Ostensibly the story of a nuclear family (pun intended) living in the generic American town of Springfield, USA, The Simpsons, as media scholar Douglas Rushkoff has noted, is really a show about media itself. The first, and by far the most literate TV show to take on mass media and its discontents as a theme, Homer and company have been deconstructing pop culture for our edification and pleasure since the gang at Community were getting meta in grade school. Be it Hitchcock movies, infomercials, the superficial and sensationalistic local news, or Thomas Pynchon novels, the show is a crash course in popular culture, nearly compulsively cataloging and critiquing other media forms.

The Tom and Jerry parody Itchy and Scratchy, for instance. That show-within-a-show obsessively watched by the Simpsons kids was dazzlingly original for pointing out—usually in bloody detail—the rather uncomfortable truth that many Saturday morning cartoon shows for kids are insanely, even sadistically violent. Having that disturbing fact about mass media confirmed by mass media is not only funny, but a profound comfort to an audience.

Al Jean was on that first writing staff in 1989. Now an executive producer with eight Emmys and a Peabody, he oversees the series' production as showrunner. Jean told us about the very unusual guest for episode 500: Julian Assange. Currently under house arrest Britain and fighting extradition to Sweden, the WikiLeaks founder recorded his cameo over the phone.

"That was a first," Jean said.

Assange joins a mind-boggling roster of guest stars who've been on over the decades, one that reads like an encyclopedia of popular culture. Bob Hope, Paul Newman, Elizabeth Taylor, Paul McCartney, Mick Jagger, Steven Jay Gould, Steven Hawking, Werner Herzog. Really. It goes on and on. Consider just the "J" section, for instance, which includes Jeff Bezos. Jasper Johns, Johnny Carson, and John Updike. British Prime Minster Tony Blair was on. While he was in office.

"That was cool," Jean said. "But we've never had a president on. Maybe that's why I was so excited about having Roosevelt this season."

That would be Teddy. In this season's second episode, "Bart Stops to Smell the Roosevelts," Superintendent Chalmers takes over Bart's education. The show features a guest appearance by, yes, Theodore Roosevelt. Sort of. Kind of. They used archival audio of the president's voice to create the impression that TR and Bart Simpson met.

Tim Long, a consulting producer, wrote the script. He explained the writing process.

"Al suggested the idea," Long said. "Both he and I had read the Edmund Morris books about Teddy, and we'd discussed them. So I think that's why he suggested it to me."