Smash hit or no smash hit, they are a ridiculous sight, two 13-year-old boys in oversize jeans (men's sizes 36 and 34) with the crotch at knee level, belts around their thighs, vast amounts of denim crumpled around their ankles. And they're wearing them back to front! With huge T-shirts and baggy quilted jackets covering their zippered behinds.

And what are two well-raised youngsters from the Atlanta suburbs doing calling themselves "Mack Daddy" and "Daddy Mack," which used to mean "pimp" when you were their age?

You watch them, Christopher "Mack Daddy" Kelly and Christopher "Daddy Mack" Smith, together called Kris Kross, and you suddenly feel as old as your own parents.

But not too old to resist a strong pop hook, as you realize when the beat bursts forth and Kelly and Smith strut across the floor, mikes in their faces, rapping for a sound check at Black Entertainment Television in Northeast. The Mack Dad'll make ya -- jump, jump! Daddy Mack'll make ya -- jump, jump! Kris Kross'll make ya -- jump, jump!

What's happening to Kris Kross is unlike anything the record industry has seen in a long, long time. It's like an act of God, a mind-boggling explosion of fame. "Jump" became America's No. 1 single in only four weeks. The video is one of MTV's most requested. The album "Totally Krossed Out," already platinum, was called "the fastest-breaking debut album {in} 25 years" by Billboard magazine.

Kelly and Smith made their national TV debut March 29 on "In Living Color." Last week, they did "Good Morning America." That's how fast they've gone from cutting-edge hip to Middle American celebrity.

How to explain it?

Well, they're cute.

While Kris Kross did a couple of tunes on BET's "Teen Summit" last weekend -- hair artfully cornrowed, smooth little faces trying to be hip-hop hard -- a few grown women watched and smiled and bobbed their heads and said, "They're cute!" And afterward fidgety teenage girls bunched together with free posters, hoping for autographs. And one cool young fellow looked at his poster and said out loud to nobody, "I'm a dude. I still want an autograph."

So it's more than cute. It's major-label hype plus packaging plus novelty plus hooks on top of cute. Peel away all that and you've got air.

But then, why do that? Why fight the universe? When something works, it works. Uh-huh, uh-huh -- jump, jump ...

Meet Kris Kross

These are hectic days for two kids who'd otherwise be sitting in a seventh-grade classroom. They're on a barnstorming promotional tour (with a tutor). They haven't even had a chance to hang out with their friends back in Atlanta since "Jump" blew up.

After BET last Saturday, they went to Richmond for a gig sponsored by a radio station. Reportedly, so many fans came out that the show was almost canceled for reasons of safety. Then Sunday night they were in Washington again to tape another TV show, this time at an Adams-Morgan dance club called Opera.

Are they tired? "No, but there's a lot of clowns out there saying we are." That's Christopher Kelly, to whom one fan referred handily as "the dark-skinned one." Sitting in a back room at Opera, Kelly seems more concerned than his lighter, slightly younger partner with affecting a hip-hop attitude, responding to an innocent question like his status was being challenged. He grips your hand with a firmness that is conscious of itself. He sometimes smirks. And when he raps over a prerecorded track of "Jump," you can hear that his voice has changed since he made the song.

Christopher Smith seems less playful. There's a seriousness in his face, a contrast to Kelly's cocksure grin.

They've known each other since first grade. Show business "was something that we wanted to do, but we ain't really think we was ever going to do it," Smith says.

"We used to rap to other people's records," Kelly says. Run-DMC, Eric B. & Rakim. "But we never made up our own raps or nothing like that."

"I wouldn't even say we was rapping," Smith interjects. "It was just like we were talking. Just saying lyrics that rhymed."

Then came the day in Atlanta's Greenbriar mall when their lives changed. They were there to buy new sneakers, but they ran into a rap group called Silk Tymes Leather and a teenage record producer named Jermaine Dupri.

"We went over to get an autograph," Kelly says. "{Dupri} asked us if we rap or dance. We told him dance a little bit, we ain't really too much rap. But he got our phone numbers anyway. We got his phone number. And he called us." Kelly was 12, Smith 11.

Dupri, now 19, is here with them. He wrote and produced every track on "Totally Krossed Out," he helped develop the whole concept, and the success of Kris Kross may do more for his fortunes than Kelly and Smith's. The man has a golden eye. Or a platinum ear. Or something.

As soon as he saw them, he thought: "Stars."

"I had never seen no little kids look like me. That's what it was," Dupri says. "They had on almost better gear than me. Almost. Fresh new sneakers. I was like, 'Wait a minute. How old are these kids?'

"From the start, they had the attitude already. They came to me with that attitude -- little kids that's got themselves together. It just needed to be polished," he says. "People might say, 'Okay, Kris Kross, they cute.' But it took like two years to get these kids together. Their rapping skills went from terrible to excellent. In four years, they should be terrors."

When the three of them are together, Kelly and Smith seem to orbit around Dupri as they would around a really cool big brother. And with his charmingly awkward smile, billy-goat beard and gift of gab, he proves to be Kris Kross's most effective spokesman.

Like a few minutes ago, when all three were being interviewed on camera by the jaunty, flirtatious "Downtown" Julie Brown, formerly of MTV, now with "Inside Edition." Kelly and Smith were kind of shy. Dupri, wearing big, sagging, backward jeans too, drew the camera right on in. "Who said {frontward} is the right way you're supposed to wear your pants in the first place?" he asked. "So now y'all know who told y'all to wear these. Fifty years, everybody'll say, 'Kris Kross said wear your pants backwards.' "

Low-hanging jeans were a fad already. Kris Kross just saw a way to give it a twist and reinforce its "totally krossed out" identity. But even in this, the kids aren't exactly original. A popular and well-packaged teenage R&B group of 1991, Another Bad Creation, employed the gimmick of wearing clothes inside-out.

Funny, then, that Kris Kross, on its album, comes out dissing ABC by name. "Don't try to compare us to another bad little fad," Kelly raps in "Jump." "Inside-out is wiggity-wiggity-wiggity-wack!"

Presumably, Dupri didn't think he had quite enough high-concept selling points to get Kris Kross over. So hey, nothing like a little trash-talking to draw attention to a new group.

"We're taking no shorts," Dupri says, explaining his swipes at ABC. But then he quickly changes the subject. When you're on top, what's the point?

"Kris Kross filled up a gap that needed to be filled," he says. "Everybody needed a modern-day Run-DMC, and here they are. They don't dance when they get on stage. People dis that walking back and forth, but we sell 100,000 records every time they do it. Just straight-up get onstage and it's about rocking the mike. No 500 people onstage, no singers."

Kelly and Smith seem to be handling the whole thing well. The toughest part? "Sound checks," Smith says after a little thought. "It's hard because you can't get that same feeling. It ain't no crowd out there so you don't know how you're gonna react to the crowd or nothing. But it's something you gotta deal with."

"The coolest thing that happened to us," Kelly says casually, "is our platinums." Their single is a million-seller, as well as the album. The trophies are on the way. "We got our golds, but we ain't get our platinums yet."

And the future? "After hanging around Jermaine," Smith says, "we came to the conclusion that we want to produce records."

Check One ...

"This one keeps punching me," Julie Brown says playfully, Christopher Kelly close at her side, as the video camera captures a group interview.

She asks the boys to describe their "dream girl."

Kelly says bashfully, "You."

Smooooth, Mack Daddy!

"Maybe that's why he keeps punching me," Brown says.

Daddy Mack's Daddy

Lunnie Smith is the man a million other parents might want to throttle if this ass-backward jeans thing catches on. He's the proud father of Christopher "Daddy Mack" Smith.

In a well-fitting suit and an unbuttoned shirt collar, Smith stands with arms folded, well out of the way, and watches the sound check at Opera. He works for the Georgia corrections department, his wife, Angela, is a bank manager, and both were "hesitant" when they heard of Dupri's interest in their son.

"You've got a small child," Smith says in a friendly but deliberate tone, "you already know what you want your child to do, you already have your plans laid out, and you're going by your plan step-by-step." And that plan is for Christopher to go to college and become a successful professional or businessman.

"At the same time, Christopher at an early age had expressed to us a desire to be in the entertainment industry. And because of that, we felt compelled to check it out."

Impressed that Dupri was a "clean-cut young man" who's "strictly focused on creating music," the Smiths gave their blessing to the fabrication of Kris Kross. In fact, Angela Smith came up with the name, remembering that when Christopher Kelly was younger, "one of his teachers called him 'Chrissy Crossy Apple Saucy' because all he would eat was apple sauce," Lunnie Smith says.

(Chrissy Crossy Apple Saucy? Id'n dat cuuute? You sure won't find that in the rapper's press bio.)

At least one of the kids' parents will be on the road with them at all times, Smith says. "We certainly feel that both have the personality, the background and the foundation to be able to handle it. At the same time, we're not naive," he says. "We understand that if you don't stay on top of it, they could easily lose that by being with individuals who don't necessarily see things the way that we see it. They're still children, they're very impressionable at this age, and we know that we have to stay on top of it."

If Christopher Smith's rap career doesn't last, maybe he can become a professional negotiator, because even before Kris Kross was created, he'd persuaded his father to allow him to wear his jeans low and baggy, despite the first "shocked" reactions of dad and school officials.

"As adults, we all had problems with it," Smith says. "{But Christopher's} main focus was that he was doing well in school, he was making good grades, and that should be what's important."

Now he declares, "We have to allow for self-expression and individuality in children. To stifle it, I think, does more harm than it does good." Which is a whole lot easier to say when your son has the No. 1 single in the country.

Smith is similarly accepting of the young Christophers calling themselves "macks," which was Kelly's idea. "It was just something boys used to use in school and stuff," Kelly explains. "Whoever gets a lot of girls and stuff, called macks."

"I believe that sometimes we as adults complicate issues more than they should be," Smith says. "These boys are having fun. As far as they're concerned, it's only a hip-hop name. While there may be another definition for a mack, they're keeping a positive outlook, so we don't see any harm."

Check Two ...

Kelly and Smith are inside a white stretch limousine in front of Opera, attracting a few black teenage boys who chill along the sidewalk.

An older white guy passes by. "Who's in the limo?"

Kris Kross, a reporter tells him.

"Christopher Cross?" the man asks, surprised and credulous.

One of the teens overhears this. "Yeah, Christopher Cross," he says. And his buddies have a long chuckle.