LOS ANGELES - Television networks are masters of self-promotion, so it's no surprise that Fox is carving out two prime-time hours tonight to celebrate its 25th year.

But why quibble over the hoopla planned for the 8-10 p.m. PDT showcase? With Ryan Seacrest as ringmaster, let's give a shout-out to the stars of "Married ... With Children," ''The X Files," ''In Living Color," ''Ally McBeal," ''Beverly Hills, 90210," ''House" and "24."

And, in center stage, the enduring "The Simpsons" and TV's great game-changer, "American Idol," are taking a bow.

It's an impressive showing for a network that's less than half the age of competitors NBC, CBS and ABC. As analyst Brad Adgate of Horizon Media sees it, Fox hasn't just met expectations, "it's exceeded them."

"Of the major networks, it's the only one that can bring in younger audiences on a regular basis," Adgate said. "They have brought out some breakthrough shows ... They've really done things that the other three networks wouldn't have done with their programming."

From a modest October 1986 debut with "The Late Show Starring Joan Rivers" and its first night of prime-time programming in April 1987, Fox weathered industry skepticism and midlife crisis ("Who Wants to Marry a Multi-Millionaire?" and other groaners) to make its case for survival and success.

Fox proved that, yes, there was room for a fourth U.S. broadcast network, three decades after Dumont dissolved in 1955 and left the Big Three networks to slice up an increasingly rich pie.

Yes, a broadcast network could shrink its prime-time lineup to the hours between 8-10 p.m. ET, allowing lucrative local newscasts control of the 10 o'clock hour, and prosper.

Yes, airing outrageously cheeky fare - ranging from clever ("Tracey Ullman") to exploitive ("Temptation Island") - would lure the 18-to-49-year-old audience that make advertisers swoon. Fox became profitable after just three years of operation, according to "Outfoxed," the 1990 book by Alex Ben Block detailing the network's birth.

That success turned competitors into copycats, extending Fox's influence across the medium.

The network's creation was "a real trial by fire for all of us," said Garth Ancier, Fox's inaugural programming chief. "My mentor at NBC, Brandon Tartikoff, thought I was crazy, and he was probably right."

The challenge: "How do we carve the audience in a different way from NBC, ABC and CBS? How do you grab people by their shirt collars and drag them over to an alternative?" Ancier said.

A key answer was development of a stable of reality shows including "America's Most Wanted" and "Cops," the latter using portable video cameras to reimagine the scripted police drama.

Rupert Murdoch, the News Corp. media mogul behind Fox, also urged his executives to look outside the U.S. market for ideas, Ancier recalled.

"He's always been an internationally focused guy and knows what's working in other countries," he said.

That global focus helped bring "American Idol" to Fox from the U.K. in June 2002, but not before Fox found itself on shaky ground, said Gail Berman, its programming head from 2000-05.

"When I came in, the network was not in particularly good shape," she recalled, with then-News Corp. President Peter Chernin cautioning her that she had to boost company morale along with ratings (although Fox had reached No. 1 with teenagers and adults 18 to 34).

"Having been the fourth network, there was a sense that being at the bottom of the barrel was an OK place to be," Berman said. "We built a great team of people that could really change the culture of 'When Animals Attack' to the culture of 'American Idol.'"

In her tenure at Fox, the network also found a new measure of scripted success, with "24" and "The O.C." among the hits, and new peer respect. In 2005, Fox earned 49 Emmy Award nominations, the most in its history, including 11 nods each for "24" and the critically acclaimed "Arrested Development," which the year before won the Emmy for best comedy series.

But it was the next wave of reality - "American Idol" and the talent contest genre - that put the ratings into orbit.

Mike Darnell is a key part of Fox's culture, past and present. Among Fox's longest-serving executives and currently president of alternative entertainment, with "Idol" part of his portfolio, his network bio proudly lists "previous hits" including "World's Wildest Police Chases" and "World's Most Amazing Medical Oddities."

He hasn't, and won't, apologize for that brand of shows. With apparent glee, he recalls how they were routinely branded by critics as "the end of Western civilization, sleazy and low-brow."

But such programming helped bolster the network in the 1990s, he said, and proved widely influential. After Fox blazed the trail, NBC aired "Fear Factor" and "Dog Eat Dog," ABC fell into the arms of "The Bachelor" and "Wife Swap," and CBS turned to "Big Brother." The progeny of "American Idol" include NBC's "The Voice" and "America's Got Talent," and ABC's "Dancing With the Stars."

So far, nobody has done it quite like Fox. While relatively staid CBS is the most-watched network, Fox ended last season with its seventh ratings victory in a row among young adults and with "American "Idol" the most-watched series for the eighth straight year.

In advance of the 2011-12 TV season, Fox brought in $2.2 billion in sponsor commitments which, for all the networks, totaled $9.25 billion, according to AdWeek. Leader CBS, by comparison, had $2.65 billion in early ad buys.

Fox's future is clouded by the same issues confronting the rest of cable and broadcast TV: an aging audience and a crowded media environment in which the Internet and other options compete for attention.

Even standard-bearer "American Idol," although still a top-rated show, has seen its eroding viewership drop by 25 percent this year and its median audience age climb to 50, analyst Adgate said. Fox newcomer "The X Factor" is scrambling to revamp its casting after a disappointing first season, while the Jennifer Lopez-Marc Anthony talent show "Q'Viva!" drew paltry ratings and was bumped from prime-time to late-night Saturday.

(Parent News Corp. has its own serious burdens, stemming from the phone hacking scandal involving Murdoch's U.K. newspaper company News International. More than 100 lawsuits have been filed against the subsidiary and an official British investigation is continuing.)

But Fox isn't ceding ground. "Glee" and "New Girl" are young viewer draws And this month, in collaboration with Fox Sports, the network launched a new tactic for long-ignored Saturday night, a mix of sports programming that's set to include NASCAR races, college football and Major League Baseball games and Ultimate Fighting Championship bouts.

"Of course, all networks mature," Darnell said. "But it's not about the network, it's about new programming. It's our nature to try to reinvent ... We usually start it, and someone else imitates us."