Adriene Hill: “The Simpsons” will air its 500th episode this weekend. Homer, Marge, Bart and Lisa have been on our televisons for 20 years. It’s the longest-scripted show in TV history. And it’s made a whole lot of people really rich. For more on its success we go to John Ortved. He’s the author of “The Simpsons: An Uncensored, Unauthorized History.” Good morning.

John Ortved: Good morning.

Hill: So why has “The Simpsons” been so successful?

Ortved: There’s a number of reasons, but ultimately it comes down to the writing. “The Simpsons” started at a time when people weren’t expecting a ton from sitcoms. “The Simpsons” was new in a lot of ways — it was animated. But also what really started to happen was the cleverness and the thoughtfulness of the humor absolutely started permeating TV and permeating the culture.

Hill: Now do you have any ballpark estimate of how much the series has been worth?

Ortved: Not really. Ballpark, a couple billion dollars.

Hill: Billion with a b?

Ortved: Yeah, billion with a b. But no one really knows. No matter what the show is worth now, when the show ends that’s when they’ll make the real money ’cause that’s when networks all over the world will pay more money to have syndicated episodes.

Hill: Now you just mentioned all over the world. What is the international market for “The Simpsons?”

Ortved: It’s not as big as you think. “The Simpsons” plays in many, many countries. But the main market for “The Simpsons” is here in America. The most interesting thing about the international market — the changes they have to make to the show so the humor translates. In the Arab world, Homer can’t have beer so he drinks soda.

Hill: Wait, so Duff is a soda pop?

Ortved: It’s soda pop. And then a foreign exchange student at Springfield Elementary is named Uter, who’s German. But in Germany it wouldn’t make sense if he’s German, so he’d have to be Swiss German.

Hill: Before I let you go, do you have a favorite episode?

Ortved: Oh my god, it’s so hard to choose. It’s like picking one of your favorite adopted children. I don’t know. I love the episode, the monorail episode, which Conan O’Brien wrote the first draft of when a monorail comes to Springfield.

Hill: I know that one. How’s the song go?

Ortved: Oh, I’m not going to sing. But he swindles the town with a song and Marge laters says that she wants to use the town’s money to fix a broken street. And Homer says to her, you should have written a song.

Hill: John Ortved is the author of “The Simpsons: An Uncensored, Unauthorized History.” Thanks.

Ortved: Thank you.

Hill: Share your favorite episode of “The Simpsons” with us.