Who knew that Homer guest-starred on "NYPD Blue" and "Friends," Lisa appeared in "City Slickers" and "As Good as It Gets," and Bart won an award for a one-woman play called "In Search of Fellini"?

Well, OK, they haven't, but their alter egos - Dan Castellaneta, Yeardley Smith and Nancy Cartwright, respectively - have done those all those things and more.

To celebrate Sunday's 300th episode of "The Simpsons," Cartwright, Smith, Castellaneta and four other members of the versatile voice cast gathered in Hollywood last month, slipping in and out of character as they talked about their long runs in one of TV's most unusual acting jobs.

With the 14th season a bit more than halfway over, Fox has signed on for two more years of the animated hit, which will kick "The Simpsons" past the 1952-'66 "Adventures of Ozzie & Harriet" as the longest-running prime-time comedy ever.

In addition to being a lucrative gig - one report, which the actors will not confirm, has each of them making $100,000 per episode - it's also a flexible one.

The series' 22 shows a year are taped two at a time every three weeks or so, leaving lots of time for other pursuits.

And if the writers decide to tweak a line after the fact, the actor in question doesn't even have to come back to the studio.

"It's, like, one of the cool things about animation," Cartwright says. "You don't have to actually be there. You can phone it in, literally."

A 43-year-old mother of two, Cartwright is a gregarious and, um, animated woman who has written a book called "My Life as a Ten-Year-Old-Boy."

Listen to her long enough, and you begin to suspect she's unconsciously picked up a few Bart-isms - "like" and "cool," for instance - in the course of her 13 years as 'toondom's most celebrated bad boy.

Like most of her castmates, Cartwright voices several "Simpsons" characters. In addition to Bart, she can be heard as whiny Ralph Wiggum, squeaky Todd Flanders and bully Nelson Muntz, whose signature utterance is a nasal "Haaah-haaah!"

When he's not dithering and "D'oh!"-ing as Homer, Castellaneta, 44, plays Krusty the Klown, Grandpa Abe Simpson, Barney Gumble, Mayor Joe Quimby, Groundskeeper Willie and a half-dozen lesser characters.

Harry Shearer handles more than a dozen, including Mr. Burns, Smithers, Principal Skinner, Ned Flanders, Otto, Rev. Lovejoy and Kent Brockman. Hank Azaria's list includes Moe, Apu, Chief Wiggum and Dr. Nick Riviera.

When Homer and his dad argue or Mr. Burns schemes with Smithers, Castellaneta and Shearer are called on to engage in lengthy dialogues with themselves. Both actors say this is not nearly as tricky as it seems.

Azaria, though, confesses he used to beg the writers not to make his characters talk to each other, "but then I watched Harry and Dan do it all the time, and I was shamed into doing it just recently."

The 38-year-old Azaria may be the only regular in the cast whose face is better known than his voice, thanks to "America's Sweethearts," "The Birdcage," "Tuesdays with Morrie," "Uprising" and "Mad About You," to whose female lead, Helen Hunt, he was briefly married.

Castellaneta recently appeared in Neil Simon's "Laughter on the 23rd Floor" and has done a comedy CD called "I Am Not Homer." Julie Kavner, 51, who voices Marge and baritone sisters Patty and Selma, has "Rhoda" and seven Woody Allen movies to her credit.

Cartwright, in addition to her Fellini play, has done Chuckie on "Rugrats," Rufus on "Kim Possible," Lu on "Mike, Lu & Og" and scores of other cartoon voices.

Shearer, 59 and amazingly versatile even by "Simpsons" standards, played dim-bulb bassist Derek Smalls in the immortal "This Is Spinal Tap" and its offshoots; impersonated G. Gordon Liddy in "Dick"; appeared in two seasons of "Saturday Night Live"; and has done political satire for years on public radio.

But whatever else is on their resumes, the actors say, people can't stop asking them about "The Simpsons."

"I think the strangest question I ever got was, do I sound like Lisa Simpson when I'm having sex," says the 38-year-old Smith, who was Marlene for several seasons on "Dharma & Greg."

Cartwright will do Bart for fans if they ask nicely: "For 10-year-olds, 11-year-olds, I go, 'Yeah, what's happenin', man?' And they're happy."

Shearer says: "The only thing that irritates me is when they ask me to do outgoing messages for their answering machine. That's where I draw the line."

Castellaneta is sometimes asked where "D'oh!" came from - and, surprisingly, he's very specific about the answer.

"Simpsons" creator Matt Groening used to write "Annoyed grunt" for Homer in the script, the actors says. When Castellaneta asked Groening for more direction, he was told to do whatever he wanted.

So, as Castellaneta recalls it, he thought back to his favorite old Laurel & Hardy shorts: "There was an actor named Jim Finlayson who used to always go, 'D'oooooooh!' Like that.

"And so I went, 'D'oooh!' And Matt said, 'Well, this is animation, you've got to go faster.' And so, sped up, it's 'D'oh!'

"I think it's actually a euphemism for 'Damn!' In the '30s, you couldn't say it until Clark Gable" (in 1939's "Gone with the Wind").