What was an unbroken record for 25 years was nearly marred yesterday. Someone -- actually something, a plump and loud rooster -- almost upstaged the morning legends Frank Harden and Jackson Weaver.

Right in the middle of Jimmy Dean's porky praise for Weaver, the announcer for a country music television show Dean did in Washington in the 1950s, a rooster crowed.

Jackson, looking to his left at this caged distraction, couldn't come up with a quip quick enough. Harden, his partner in news and jokes on WMAL-AM for the last quarter-century, reddened and laughed. Then Dean, the prince of sausage, country and corn, said, "I have known every kind of critic. But that was damn well ridiculous."

And the rooster crowed again.

But experience won. The live broadcast of Harden & Weaver's 25th anniversary show went on without ruffled feathers. And even the bird, who continued through the appearance of actor-singer Burl Ives, was finally -- like all of Harden & Weaver's competition -- pushed to the side.

Yesterday's show was a celebration of the longest-running morning team in radio and more: domination of the all-important morning "drive time" in Washington, a monumental record of fund-raising that has netted more than $4 million for Children's Hospital, years of topical routines, endless school closings, homespun community announcements and a limited supply of music.

What have Harden & Weaver been dishing out for 25 years? Reliability, said the pair, sitting in their studio after a recent show. Years ago, their fans started calling them a utility, just like electricity and water, and that's a description they embrace.

"This town is not a flash-in-the-pan town -- maybe it is for politicians," said Weaver. "But for air people, the longer you are here, the more you are part of the woodwork, the more you are part of people's minds." The diminutive Weaver does the memorable characters, such as the nameless high-pitched lady and the senator. (Weaver has also appeared on a number of network shows and is the voice of "Smokey the Bear.")

They avoid editorializing. "If you take one side of any issue, then you have alienated half your audience," said Harden. "We are not in the alienation business." The tall, bespectacled Harden has a silvery mane worthy of a distinguished statesman.

What they practice, Harden quipped yesterday, is "dynamic inaction." But their show is a spontaneous melody of quick timing, topical responses, family-style humor and characters the audience loves.

"It's old-time radio," said Weaver.

It's hard to believe, but one character, Boscoe Osgood, has been getting letters for 20 years.

"He's a special-events reporter who never gets to the right place," said Harden. "When the Olympics are in Sarajevo, he shows up in Los Angeles. And he's started getting letters from soneone who signed herself Pamela. She is madly in love and puts us down because we wouldn't provide him with resources to get to where she is. And this person is in the airlines or travel business because we get letters from Bombay, Paris, Maine, Norway."

Weaver, who hails from Buffalo, has logged 42 years with WMAL. Harden, a native of Macon, Ga., has worked at the station for 37 years. From 1950 to 1953 they had a 15-minute, three-times-a-week show. In 1960 they started as a morning team on their first 13-week contract. They just signed a six-day-a-week contract that Weaver said ties them to the station "until forever or Armageddon, whichever happens first." ABC, the owner of the station, gave each of them a check for $25,000 this week.

They have lively opinions on the changes in radio:

On announcers: "A disc jockey is a guy who has learned to speak without using verbs," said Harden. "We feel we are communicators," said Weaver.

On consultants: ". . . guys selling medicine off the back of the truck," said Weaver. "We try to ignore those people as much as possible," said Harden.

On the ratings systems: "This is the greatest monkey on anybody's shoulder, in fact it's a gorilla" (Weaver).

To hear them tell their story, radio has been a wonderful life. They've had their angry listeners (one slammed down the phone after telling them that newscaster Paul Harvey, who is carried on the show and is a target of some mild teasing, was a "better American" than they were). And they have made mistakes on the air. Once Jackson said "Garlius Jewlfinkel," in- stead of Julius Garfinckel, causing the department store to temporarily pull its ads. Harden, who suffers from a back problem, has had several health crises.

Their coworkers have some tall tales. Bill Mayhugh, the overnight announcer, said, "For 20 years I have seen them at 5:30 a.m. Each day at 5:30 Frank has told me a slightly obscene joke. And at 5:35 I have to explain it to Jackson. Then Frank reads the paper and Jackson has something odd to eat like a toasted kumquat sandwich. The bread is not toasted. The kumquats are."

Whatever their working habits, they love their jobs. "I have an attitude that if a day ever comes that I don't look forward to coming into this radio station, it's the day I quit. I look forward to it," said Harden.

And why shouldn't they be content? Their audience seems to be replenishing itself. "We are into the second generation, and the third is coming along. We are growing our own audience," said Weaver.

"We have an audience farm," added Harden.

The generations were in evidence yesterday. John Everhard of Vienna, who had attended every anniversary party since year five, was wearing a boating hat with "Harden & Weaver" printed on it, and taking Polaroid pictures. Joe Mills, who works for AT&T and has been listening to the duo for 20 years, had taken the day off to drive down with his father Joseph from Dickerson, Md. And Isolde Chapin, the director of Washington Independent Writers, had her daughter Laura Silberman and her granddaughter Mallory Silberman in tow.

Dependability is what the listeners say they get. "You got the time, the weather, a hymn, a march, what else do you need," said Mildred Rhodes, a retired government employe who has been listening for 25 years. Yesterday the hymn was "Amazing Grace."

"I know exactly which stage of dress or undress I should be at when the hymn is played," said Doris Rucher, a listener for 15 years who stopped by on her way to work. "And I know I should be out of the house by the march." Yesterday, the U.S. Combined Service Band played the Armed Forces medley from "Anchors Aweigh" to "The Caisson Song."

Best wishes came from President Reagan and Vice President Bush on separate tapes. There were personal messages from Rep. Michael Barnes (D-Md.), Fairfax County Board Chairman Jack Herrity, former Redskins Sonny Jurgensen and Sam Huff and current player Mark Murphy, astrologer Jeane Dixon, sports czar Abe Pollin, cultural czar Roger Stevens and about 1,000 listeners. The night before at a reception at the Mayflower Hotel, the Rev. Gilbert Hartke stopped by, as well as a lot of advertisers and media personalities.

"I listen to you at 6 a.m. each morning," said Jurgensen, joining Harden, Weaver and Huff yesterday on the steps of the Kennedy Center Concert Hall. "Yeah, when he's going home," cracked Huff.

Standing in the back with a box top attached to a golf club and inscribed "Harden & Weaver for president in 1988," Bob Farber was pushing his cause. "I've heard Congressmen Bill Ford and Dale Kildee and Senator John Glenn quoting them. I figured it was time they ran," said Farber, an international trade lobbyist. "They are able to joke about themselves and if you don't laugh at yourself, you can't survive in Washington."

Just then the rooster crowed again.

And someone unfurled a banner: "Still Crazy After All These Years. Happy 25th!"

And Abe Pollin presented them with an engraved ring, following a "wedding ceremony" in which Weaver promised to "only mention the Jack Tar once a week rather than every half hour." And Harden promised "not to sell the movie rights of our book to Larry Flynt." And both promised "to be faithful, creative and supportive till rating days do we part."