The arranged marriage between UPN and The WB, which will result in one strangely named network - The CW - next fall, throws together a pair of oddly disparate mates who otherwise never would have been caught dead together.

For more than a decade, the two so-called “netlets” not only were vicious rivals, but they also ran in totally different social circles. The WB was the knockout babe - or hot hunk - everyone wanted to be seen with at parties. Meanwhile, UPN was the bumbling little geek who kept finding ways to embarrass himself in public.

Yes, that’s a broad generalization (there were times when UPN outshone its rival), but reputations have a way of sticking. The WB, after all, spawned “Buffy the Vampire Slayer” and “Dawson’s Creek,” and was a major force in shaping America’s youth culture. And while UPN did earn kudos for catering to African-American audiences, it largely will be remembered as a wildly spastic entity that gave the world cheesy “Star Trek” makeovers, bogus wrestling and a freak show called “Chains of Love.”

In the end, though, both part-time networks shared a fatal flaw: Try as they might, they couldn’t consistently generate profits, much less big-league ratings. And so, it seems, they really do need each other.

By combining forces, their backers hope to form a major network that will stand tall in a crowded TV universe. The first step in that quest comes on Thursday when CW bigwigs present their new fall schedule to advertisers in New York.

The lineup is expected to feature a blend of the most popular holdouts from The WB and UPN (think “Gilmore Girls” paired with “Veronica Mars”), as well as a few fresh offerings that will be targeted at teens and young adults.

But there’s also a downside to the consolidation: A number of established shows won’t make the cut, and consequently, certain viewers - mainly African Americans - will lose out.

UPN airs eight sitcoms largely made up of black actors, more than any other network. Speculation has it that seven of those shows - “One on One,” “All of Us,” “Cuts,” “Eve,” Half & Half,” “Love, Inc.” and “Girlfriends” - are considered to be on the “bubble.” The lone exception is Chris Rock’s comedy, “Everybody Hates Chris.”

A trip back in time reveals that both The WB and UPN initially embraced minorities in an attempt to find their niche. Following the early playbook of Fox, The WB offered shows such as “The Parent Hood” and “Sister, Sister” and introduced America to Jamie Foxx and Steve Harvey. Among UPN’s early crops were “Moesha” and the infamous “Homeboys in Outer Space.”

But just as Fox did, The WB eventually moved toward shows with broader appeal among young audiences.

By the 1998-99 season, the achingly overwrought melodrama “Dawson’s Creek” was a sensation among the teen viewers coveted by advertisers, as was the offbeat “Buffy” and the piercing freshman drama “Felicity.”

In addition, The WB was proving, with the robust hit “7th Heaven,” that there still was a market for wholesome family programming. Suddenly The WB was being perceived as the hip destination, despite a dubious decision to deploy a frog from a 1956 cartoon as its mascot.

Meanwhile, despite early success with “Star Trek: Voyager,” UPN didn’t seem to know what it wanted to be. At one point, it dropped its full-family ambitions in favor of a narrower young-male audience, while simultaneously trying to court minority viewers.

Things got so bad for UPN that detractors gleefully searched for new ways to deride its call letters. The network became known as the “Utterly Pointless Network” or the “Used Parts Network” - the latter a reference to UPN’s penchant for latching onto hand-me-down programs (“Buffy,” “Roswell,” “The Hughleys”) from other networks when its own cupboard ran bare.

But few public relations blunders could top “The Secret Diary of Desmond Pfeiffer,” a 1998 UPN sitcom about the fictional black butler of Abraham Lincoln. Tasteless and bawdy, the show drew the wrath of the NAACP and, mercifully, was axed in less than a month.

“Pfeiffer” proved to be a low point in UPN’s up-and-down relations with black audiences. The network, over the years, has received justifiable praise for featuring black actors more prominently than any other broadcaster (see: “Girlfriends,” “Everybody Hates Chris” and “Eve”). But critics, including “Boondocks” creator Aaron McGruder, also have taken UPN to task for a preponderance of low-rent sitcoms that dabble in broad humor and racial stereotypes.

Not that The WB could boast of a great track record when it came to diversity.

In its relentless quest for youth cred, the network stocked its shows - especially the dramas - to the brim with young and gorgeous people, turning them into instant heartthrobs. Trouble was, The WB’s idea of beauty seldom extended to minorities. The slight, in effect, closed the doors to a large chunk of America.

In recent years, fewer people have bothered to knock on The WB’s doors anyway. America’s youth, it turns out, are a fickle bunch, and the network’s formula for drama success apparently has worn thin.

Not since “Gilmore Girls” (2000) and “Smallville” (2001) has The WB produced a truly buzz-laden drama. As for WB sitcoms, well, don’t make us laugh.

Surprisingly, it’s UPN - with no amphibious mascot to speak of - that has developed more traction in recent years. Shows such as “Everyone Hates Chris” and “Veronica Mars” have been embraced by critics, and the reality franchise “America’s Next Top Model” is a legitimate phenomenon.

Still, it’s not enough to bolster an entire network. And it’s not enough to dislodge a long-entrenched inferiority complex. That’s why UPN and The WB are tying the knot.

Until death - and/or really bad programming - do they part.