You’ll never rap alone

If there were a superhero named 50 Cent, his costume would not be a cape but a blue bulletproof vest. His motto would be a remix of the rapper’s album title: “I got rich and didn’t die trying.”

This would be 50’s legend: In an ailing music industry, he breaks records in a single bound, selling 872,000 albums in one week and releasing “In Da Club,” now in its fifth month on the Billboard charts. The superhero’s sidekick would be a scowling, quick-tongued, white-T-shirt-wearing blond guy. Together they would launch a ceaseless crusade against “fake” gangstas everywhere -- especially the nefarious Murder Inc. rapper Ja Rule.

The superhero 50 Cent would have grand powers, including the ability to resurrect the dead and record duets with them, one with the Notorious B.I.G. and one with Tupac Shakur. Superhero 50 would have nine lives, just as the rapper, who wears gangster scars like a halo, once took nine bullets and did not die.

But -- and here I speak with tongue firmly out of cheek -- the greatest power possessed by our 50 Cent hero would be his omnipresence. It’s a feat he’s already accomplished, first by recording an album so chock-full of catchy tunes, it gave hip-hop radio an unspoken motto: “all 50, all the time.” Only a superior rapper could make bullets and bravado so irresistibly and so cheerfully melodic: Any man who doesn’t joyously hum along to “P.I.M.P.” or “Many Men,” two thematically un-joyous tracks from “Get Rich or Die Tryin’, “ is a profoundly un-joyous man himself.

But there are only so many songs on a record, and even radio superhits like “In Da Club” have a shelf life. Although hip-hop may have unofficially been renamed “The 50 Cent Show,” other rappers still clamor for airplay. Put these facts together, add the truism “if you can’t beat him, join him” -- and you’ve explained hip-hop’s hottest new commodity: the 50 Cent duet.

It’s come to this: Show me the rap or R&B; artist, and I’ll show you his or her 50 Cent duet. Some of these duets appear on albums, while some appear on hip-hop’s other 50-Cent-inspired product, the mix tape. Some have been sanctioned by the 50 Cent camp; some have been shunned by it; others have eluded it. (“There’s a Sean Paul duet out? I can’t keep track. You’re best off going to Canal Street,” sighed one of the rapper’s publicists, referring to the CD bootleg capital of New York.)

Keeping track of hip-hop these days is about keeping track of who’s teamed up with 50 lately -- or, better yet, who hasn’t. (I’ll register my requests: rapper Nas and Britney Spears, please.)

Partners from beyond the grave

Official duets appear on 50 Cent’s album. There’s his current hit with singsong rapper Nate Dogg, “21 Questions,” and “Patiently Waiting” with Eminem, whom 50 calls “my favorite white boy.” One of the more plodding tracks on “Get Rich or Die Tryin’, “ “Patiently Waiting” pits 50’s slurred, off-kilter rhymes against Eminem’s high-pitched whine. Some of us were patiently waiting for anyone to dismantle Slim Shady’s radio monopoly -- and along came 50.

Ever popular during a hip-hop era steeped in nostalgia is the 50 Cent “hip-hop martyr trilogy”: duets featuring and/or inspired by rap legends Notorious B.I.G. and Tupac. Critics can’t agree on which deceased rapper is best compared with 50 -- He’s Tupac! No, he’s Biggie! -- and fans can’t agree on which gangsta is the “realest” one of all. Thanks to two singles on New York DJ Whoo Kid’s mix tape, you can make the call.

50 and Biggie’s duet is a bouncy track that, unsurprisingly, made waves on New York radio and concludes -- thank goodness! -- that both Big Apple rappers are “real.” “The Realest Killas” joins 50 and Tupac. Backed by drumbeats and sporadic gunshots, the track is a call to arms against Ja Rule, the rapper whom 50 accuses of being a Tupac knockoff. In contrast to 50, who deems himself “the real Tupac.” You’ll find more “reality” mania here than on prime-time television.

The much-hyped 50-Ja Rule feud also fuels track three of the “R.I.P. trilogy,” “Hail Mary 2003,” DJ Kay Slay’s version of a Tupac Shakur song that has 50 and Eminem sounding more intense than ever. The track reaches its climax when genial rapper Busta Rhymes, sporting uncharacteristic verbal venom, adds his anti-Ja verse. Busta, whose car was recently riddled with bullets in front of Violator Entertainment, which also manages 50 Cent, has apparently taken a break from passing the Courvoisier to tell Ja he’s to blame.

Confused? 50 Cent feuds have grown more complex than Watergate, making it near impossible to keep track of who’s pitted against whom. Battle songs (or “diss tracks”) multiply like mix tapes; most amusing are the anti-50 ones (Ja Rule’s version of “Wanksta,” or Queens rapper Cadillac Tah’s “There’s a Snitch in the Club”) that simply reword 50 Cent hits -- thereby offering our superhero’s beats yet more air time.

Good-time duets too

Lest he grow battle-weary, 50 keeps the good-time duets coming. There’s “Real Rude Boys” with Sean Paul, which has Jamaica, Queens, beside Jamaica, West Indies. Reggae poster-child Paul emerges as the spiciest 50 Cent side dish yet (a good thing, as the two will tour together this summer).

The award for “most over-the-top 50 Cent duet” goes to the remix of “P.I.M.P.,” for which 50 enlisted the realest players of all: Snoop Dogg and his sidekick Don “Magic” Juan (an actual retired pimp). On the riotous Whoo Kid track, which seems indigenous to West Coast radio, 50 deems himself a “p-i-m-p,” Snoop deems himself a “C-r-i-p,” and laughing listeners can’t help but “f-l-i-p” over this one.

50 also rears his head on an irresistible Mary J. Blige track, DJ Kay Slay’s “Let Me Be the One,” and on the most memorable 50 Cent duet to date: “Magic Stick,” with the ever-salacious Lil’ Kim, from her recent album. Something about this track makes it the ultimate guilty pleasure: Its carnivalesque tone? Its bouncy feel? Its oh-so-original use of metaphor (50 has a “magic stick” and Kim a “magic box”)?

The pure joyfulness of “Magic Stick” says something about the clamor to jump on record with 50 and the secret of his success: a smile. Hip-hop doesn’t need another gangster who takes himself seriously at all times, on all tracks. After all, even superheroes need a good guffaw every now and then -- especially when they’re laughing all the way to the bank.