It's a typical weekday morning and you're driving to work, distractedly switching from one radio station to the next.

First stop: A commercial seems to be playing. You're about to turn to another station but something sounds a bit strange... .

A man with an ordinary voice is saying: "So, it's 3 in the morning, the phone rings. It's some guy from MCI tellin' me how AT&T charges too much for long-distance, and how he can save me all kinds of money. So I tell him put it in writing. Silence. I go back to bed and then the phone rings again! Hello. This time it's a guy from AT&T. He says that when an MCI operator is talkin' to me real friendly and all, she's flippin' me the bird at the same time! She is? So by now it's 3:30, and just as I'm dozing off, the phone rings. Now I'm getting steamed. What! It's the guy from MCI again. He says, 'Sure AT&T gives instant credit, but they're getting the money from widows and orphans!' They are? So just as I'm about to slam the phone down on him, somebody knocks on my door. It's a guy from Sprint! He says AT&T is secretly shipping A-bombs to Iraq, MCI is burning down rain forests when they're not too busy killing dolphins ... and that all the Sprint operators work in the nude. Why can't they leave me alone?"

Then a real commercial comes on and you move on.

Next stop: A dance-music station also seems to be running a commercial. But upon closer inspection...

"Pillsbury -- for years a trusted name in baked goods," intones a soothing female voice. "Now Pillsbury is your trusted name in home health care. Introducing the Pillsbury Pop 'N' Fresh Pregnancy Test. The fastest pregnancy test available. If the dough rises, so will you. ... Because nothin' tests lovin' like a bun in the oven."

You tune in another station and recognize the rapping riffs of Vanilla Ice's hit tune "Ice Ice Baby." But the song turns out to be "Rice Rice Baby," chronicling one man's comical adventures in Chinese dining.

Many listeners no doubt assume that morning radio personalities -- who are commonly paid seven-figure salaries for their on-air charm and comedic abilities -- produced these parodies themselves. But, like Johnny Carson or David Letterman, who have a host of writers preparing their monologues, high-profile disc jockeys also have a stable of writers and producers behind the scenes turning out funny material.

And while some of them are on the station's staff, others are working thousands of miles away and not only don't know the deejays, they may not even know the deejay's name. They are part of a little-known cottage industry of about 20 syndicated comedy services that each week churn out several dozen slickly produced sketches and song parodies for hundreds of subscribing radio stations across the country.

"We're a best-kept secret," said Andy Goodman, president of American Comedy Network, based in Bridgeport, Conn. "In the radio business we're pretty well known. But if you go outside the radio business, no, people haven't heard of us."

Many of the parodies heard on contemporary hit stations are created by the top services: American Comedy Network, Premiere Radio Networks and Olympia Comedy Network.

The reason is simple: The morning deejay has got to fill three or four hours every day with new material.

"Unlike a stand-up comedian, who can do the same thing each time he's on stage, {a radio deejay} has to be fresh and incorporate current events," said Tim Kelly, president and co-founder of the Hollywood-based Premiere Radio Networks. "He's got to make it funny, got to make it current, got to make it move."

In big cities like Los Angeles, where radio is a multi-million-dollar business and competition for listeners among 80 outlets can get ugly, stations must find creative ways to distinguish themselves.

"The reason they come to us is because it's a desperate battle," said Kelly, a former KIIS deejay in los Angeles. "Morning shows need to be funny and it's tough coming up with comedy day-in and day-out starting at 6 in the morning."

Comedy services arose over the past decade with the growing popularity of the "morning zoo" format. Scott Shannon, program director and morning show deejay at KQLZ in Los Angeles, was one of the pioneers of the fast-paced style, in which humorous bits are interspersed with music, news and chatter.

"I had this concept in my head and it was a combination of 'The Tonight Show,' 'Saturday Night Live' and a talk-radio show mixed in with music," Shannon said. "Radio had gotten too serious at about this time. Contemporary radio was pretty much devoid of personality. They'd also banished from the radio novelty songs and parodies, and I've always collected those, along with a collection of comedy routines."

Shannon started playing his comedy albums on the Tampa station on which he was morning deejay. "I noticed some of the songs caught on with the younger listeners," he said. "I found I'd hit a nerve."

Soon he and his "morning zoo" format were off to New York. Just as soon, he said, "the zoo concept just got lifted around the country."

Suddenly he was receiving tapes from wanna-be comedians. One of them was from David Kolin, a dental student whom Shannon describes as "one of the first to service this exploding industry of comedy radio shows."

Said Kolin: "Where my business came about was that morning shows out there require a huge support staff to be really cutting edge. I was able to build a studio that's sophisticated enough to do anything, which I think is beyond the capabilities of a typical station house."

Today, as president of DB Communications in New York, Kolin enjoys a reputation for turning out some of the most slickly produced commercial and song parodies. "The Andy Griffith Show" is a favorite subject for takeoffs, such as a recent one promoting "Rocky Fife," with a Don Knotts sound-alike doing Sylvester Stallone. He spoofed the Milli Vanilli tune "Blame It on the Rain" as "Blame It on Hussein" and produced a phony ad for the Elvis Talking Pillow: "Ladies, are you lonesome tonight? Tired of sleeping alone? Now you can sleep with the King. Hear him whisper romantic things like {in Elvis' deep tones}, 'Do you think Domino's will deliver this late?' and 'Do you like your eggs regular or extra crispy?' "

Yet for all their production skills, radio comedy writers and performers go largely uncredited.

"Listeners really think that these people are there in the stations," Kelly said. "It's theater of the mind. That's what it's all about. The idea is to make the {disc jockeys} stars in their own environment. That's what we're in business for."

But a little recognition wouldn't hurt, others say.

"It can be frustrating, because you feel like you're operating at a very high level but nobody knows you," said American Comedy Network's Goodman. "It's frustrating when you see a skit on 'Saturday Night Live' and everyone's talking about it and it is pretty similar to what you do."

In much the same way that "Saturday Night Live" functions, the bigger services employ a staff of writers and producers who meet regularly to develop ideas for sketches, then write and perform them.

Premiere staffers get together every couple of weeks over lunch at a neighborhood pizza parlor and toss around ideas for parodies, Kelly said. A core group of about eight people quickly write the material and put it together in the company's production studios. The comedy sketches are then "auditioned" for Kelly and a creative vice president, who decide what will go out to subscribers.