Bart Simpson is acting like himself, which is to say naughty. And he sounds like himself, with that familiar mischievous lilt.

But Bart's voice is coming out of a petite blonde wearing a fluffy, bright-pink wrap. Dumpy Homer has morphed into a lanky fellow, and mom Marge's towering blue hair is brown and tastefully cropped.

The event was a "table read," when the cast of "The Simpsons" gathered with a roomful of writers, producers and guests, using their imaginations to conjure up the animated family with the distinctive mustard hue.

It was just one of the steps toward crafting an episode of the Fox series that begins its 16th season Sunday at 8 p.m. EDT with its annual "Treehouse of Horror" special. The run is remarkable for any show — but especially for one like this.

Irreverent, witty and willing to take on anything from politics to religion to family values, "The Simpsons" has provided a rare bit of spice for the oatmeal-bland bowl of TV broadcasting.

The table read, held in an oversize trailer at the Twentieth Century Fox (search) studio where the series is produced, itself is a symbol of the show's enduring popularity. A decade ago, it finished the season as the 67th most-watched show; it was No. 69 last season with 10.7 million viewers and won its time period among the coveted 18 to 49 age group.

Actors, producers and writers sit at a massive conference table littered with water bottles and note pads. Invitation-only visitors ring the table. (Noticeably absent are the network executives who always haunt rehearsals; "The Simpsons" has a rare stipulation, won by executive producer James L. Brooks (search), limiting Fox meddling.)

"It's sort of the hottest ticket on the lot," said Yeardley Smith (search), who voices young Lisa, the wise Simpson daughter.

"I'll look around and go, 'Hey, there's Elvis Costello (search),'" said Al Jean, an executive producer who's been with the series since it was spun off in December 1989 from Tracey Ullman's Fox series.

Singer-songwriter Costello, who provided his voice for one episode, popped up at the table read for another.

"People often come for the fun and bring their children," said Jean.

It's a treat for observers but serious work for the cast and producers. This is the first time a script has been performed after months of writing and revision.

This particular week it's also the first time the actors have seen the script. Finished at the last minute, it couldn't be provided until the cast arrived at the studio for the rehearsal last Thursday.

The assembled performers include Smith; Dan Castellaneta (search), who received his third Emmy this year for voicing Homer and whose other characters include Krusty the clown and Grampa Simpson; Nancy Cartwright (search) as Bart; Julie Kavner (search) as Marge; and Harry Shearer (search), who does an array of voices including Ned Flanders and Mr. Burns.

Absent is Hank Azaria (search), who was in New York rehearsing a new musical. Azaria's characters, including convenience store owner Apu and police Chief Wiggum, are voiced for now by another actor.

They're working on an episode that won't air until next season, typical for a labor-intensive animated series. A roughly 21-minute episode takes about nine months to create, including the animation work done domestically and in South Korea.

In the script at hand (written by Danny Chun), Marge and Bart are engaged in unusual mother-son bonding, breezing through Springfield on a tandem bicycle and singing "Sweet Home Alabama."

Marge: "I can't remember our last outing together."

Bart: "It was to see that court-appointed psychiatrist."

Marge: "Oh yeah. He should never have let you near that letter opener."

The actors move briskly through their lines and most of the jokes draw guffaws from the room. But one shaggy-haired figure proves a tough customer, rarely even smiling — series creator and executive producer Matt Groening.

"He's not an easy laugh, so when you get a laugh out of him you feel like, 'Yes!' It's a big deal," said Smith.

Groening follows the script carefully, jotting down notes for the writers. Among his suggestions: omit a giggle from baby Maggie Simpson in one scene, and beef up another in which Marge finds herself without a partner for her new bike built for two.

"He wanted more of a visual with Marge being lonely, so we put in a parody of 'Midnight Cowboy' where Marge and the bicycle are walking around Springfield to that harmonica music," Jean said.

After all these years, Jean has developed his own script shorthand: a check mark for a joke that gets a laugh, an "X" for one that falls flat. "Something that's sweet but doesn't necessarily get a huge laugh will stay in," Jean said.

After all these years "it's a fairly well-oiled machine," observed Smith. Actors who are out of town, like Azaria, can record their lines at a convenient studio.

When the cast is finished the animators step in. The Los Angeles-area animation house Film Roman creates a black-and-white draft, called an animatic, which reveals what works and what doesn't, Jean said.

"Sometimes we do a considerable rewrite with the animatic. Once it's in color, the cost of changing too much is prohibitive," he said.

The revised animatic is sent to South Korea for creation of the final version — or almost final. If a line remains troublesome, the characters' lip movements provide enough leeway for another phrase to be subbed in.

No matter what changes, though, the characters stay the same.

"It's a bratty boy and a sensitive, intellectual girl and a dumb but well-meaning husband and a wife who's sweet and knows a little better than him," said Jean.

The show remains a success overseas, airing in Europe, Asia, Africa and elsewhere. A reinvigorated marketing push expanded the multimillion-dollar "Simpsons" brand of products in recent years, with hundreds of companies worldwide selling figurines, board games, apparel, snacks and more.

Just how durable is "The Simpsons," which has the cast signed through season 19? There will be a 20th season at least, Jean figures, allowing it to match "Gunsmoke" as the longest-running scripted show in prime-time.

Can the comedy keep its spark? He points to the latest table read as assurance.

"I thought it still rang true and was funny," Jean said.