After 29 seasons, fans know a lot about “The Simpsons,” but they haven’t heard it the way Mike Reiss tells it in his new book “Springfield Confidential: Jokes, Secrets and Outright Lies From a Lifetime Writing for ‘The Simpsons‘ ” (Dey Street, $27.99).

Reiss has been with “The Simpsons,” with some breaks, since its uncertain beginning, when fellow writers thought the animated comedy would last only six episodes.

Sam Simon, the late executive producer who developed the series with creator Matt Groening and James L. Brooks, was the optimist: He predicted 13.

More than 630 episodes later, the Emmy-winning Reiss, a former head writer who remains part of the writing staff, has plenty to say about the animated classic.

“Springfield Confidential” is full of humorous asides and fun facts, including 23 steps to making an episode — and why the characters are yellow. Reiss expounds on favorite episodes and memorable guests (including one he considered a diva: “To protect her anonymity, the publisher’s legal department will only let me give you her first name: Oprah.”).

Author Mike Reiss and his cartoon doppelganger.

Author Mike Reiss and his cartoon doppelganger. | Provided photo

Here are seven insights from the man who accidentally leaked plans for 2007’s “The Simpsons Movie” yet lived to write again:

The first episode, “Some Enchanted Evening,” was a disaster.

But the second, “Bart the Genius,” in which the proud underachiever switches test scores with smarter classmate Martin, was much better. That became the series premiere — after a December 1989 Christmas special — and “Evening,” which featured the Babysitter Bandit, closed the first season.

"The Simpsons" writers, a predominantly male group, are more like brainy Lisa Simpson than rebellious brother Bart.

“The Simpsons” writers, a predominantly male group, are more like brainy Lisa Simpson than rebellious brother Bart. | Fox

The writers identifies more with Lisa Simpson than brother Bart

“None of us were Barts when we were kids,” Reiss writes. “We were all Lisas, good, hardworking students with very few friends. And then one day we woke up, and we’d become bald, paunchy Homers.”

A happy writers’ room, with a sliver of tension

Reiss speaks well of his colleagues and says the writers’ room has “a small-town feel, like a Mayberry or a … Springfield.” But there was early discomfort. Simon, who left after a couple of seasons, was “miserable” that Groening seemed to get all the credit. He channeled his bitterness into 1991’s “Flaming Moe’s,” an episode in which bartender Moe takes credit for Homer’s drink creation.

Mike Reiss, this is your comedic life

Besides contributing a zillion jokes, Reiss has been immortalized on “The Simpsons,” not always voluntarily. In 1992’s “Lisa’s First Word,” Homer builds Bart a bed with a nightmare-inducing clown face on the headboard. Reiss’ father once built his brother a scary clown bed. Mr. Bergstrom (voiced by Dustin Hoffman), the ideal teacher in 1990’s “Lisa’s Substitute,” is named for one of Reiss’ teachers. Simon based Bergstrom’s appearance on Reiss.

"Springfield Confidential: Jokes, Secrets, and Outright Lies from a Lifetime Writing for The Simpsons," by Mike Reiss with Mathew Klickstein.

“Springfield Confidential: Jokes, Secrets, and Outright Lies from a Lifetime Writing for The Simpsons” by Mike Reiss with Mathew Klickstein. | Dey Street Books

The evolution of Apu

Reiss likes Indian Kwik-E-Mart operator Apu, a smart, pleasant man and “the only person in Springfield who works hard at his job.” Writers treated Apu, at times the only Indian character in prime time, with “depth and dignity,” but now many complain he is a stereotype, culminating in “The Problem With Apu,” which Reiss calls “a nasty little documentary.”

He says Apu has become a problem for the show and that Hank Azaria, who is not Indian, now is reluctant to portray him.

“We’d hate to lose a beloved character from the show. But times change, and maybe after three decades, time has run out for Apu.”

Sideshow Bob, right, terrorizes, Bart, as usual, in "Cape Feare," a 1993 episode of "The Simpsons" that featured a classic stepping-on-a-rake scene.

Sideshow Bob, right, terrorizes, Bart, as usual, in “Cape Feare,” a 1993 episode of “The Simpsons” that featured a classic stepping-on-a-rake scene. | Fox

Comic genius born from necessity

Some of the show’s greatest moments began as time-fillers. When one episode ran short, Reiss and onetime writing partner Al Jean, now in charge of the show, wrote an extra-long “couch gag,” opening the door for many creative renderings of the introductory segment. When 1993’s “Cape Feare” needed padding, Jean extended a sequence in which criminal clown Sideshow Bob steps on rakes, turning “a slapstick joke into a surreal classic.”

Thee people said no to being guest stars

Over the years, 725 guest stars have appeared, from Stephen Hawking and three of the Beatles to Larry King, Joe Frazier and Elizabeth Taylor. The few who have turned down an invitation include Bruce Springsteen, Tom Cruise and every U.S. president from Gerald Ford to Barack Obama.

Contributing: AP