Maybe it's the eyes. China-white saucers punctuated by dark-as-night centers.
Maybe it's the shimmering gold teeth. Sharp as an ax and framed by a bushy black beard.
It could be the arms. Defined by impossibly thick muscles and quick as a rattlesnake strike.
Something -- maybe all of the above -- helped to transform Kimbo Slice from bare-knuckle, backyard brawler into one of the leading attractions in mixed martial arts.
Yet his biggest appeal, simply put, might be a knack for toppling large men with one powerful blow.
"He's the closest I've come to Mike Tyson," said Gary Shaw, who promoted the former heavyweight boxing champion and now does the same for Elite Extreme Combat, an MMA organization based in Los Angeles.
Those who have not heard of Slice, or never downloaded one of his immensely popular underground fights, can witness for themselves tonight, when he's scheduled to take on fellow heavyweight James Thompson in the main event of a card scheduled to be televised on CBS.
Tape-delayed on the West Coast, the broadcast from Newark, N.J., will be the first MMA event ever shown on a major network. To help viewers who may not understand moves like a guillotine chokehold, the network plans to mix in explanatory features, including the sport's rules and why it is staged inside a cage.
For his part, Slice makes it clear he is ready for prime time. Yet, as much as he plays off his power, strength, even his considerable charisma, that is not all he is.
"He has an on-off switch," Shaw said. "If it's off, he can baby-sit your kids, everything's great. If you flip that switch on, it's a problem."
Out of the cage, away from his push to intimidate merely by being there, away from the controlled acts of violence, Slice surprises.
Those who know him say he is soft-spoken, articulate, loyal, humble and prides himself on being a loving father of six children.
"He will walk me and my wife out to a vehicle, stand by the vehicle until the door's locked and the vehicle pulls away," Shaw said. "I sit there in utter amazement because he's a superstar."
Even fellow MMA fighters are caught off guard by this side of Slice.
"He's way more educated and smarter than I thought he'd be," said Scott Smith, who is scheduled to fight middleweight Robbie Lawler on the same card tonight. "Looks aren't everything, I guess."
Not everyone, however, is applauding EliteXC for introducing Slice to the MMA world, let alone a mainstream television audience.
Dana White, president of the rival Ultimate Fighting Championship, said a number of his fighters could defeat Slice, and Slice's arrival is hardly "putting MMA's best foot forward."
"This guy was fighting in backyards a little while ago," White said. "When we were bleeding millions of dollars, it would have been pretty easy for us to put on a freak show."
Slice, of course, does not see himself as a freak.
The 34-year-old fighter, whose real name is Kevin Ferguson, caught fire with the MMA 11 months ago, defeating former heavyweight boxer and Olympic gold medalist Ray Mercer with a first-round guillotine chokehold.
Five months later, he made his debut with EliteXC. Nineteen seconds into his first Elite bout, Slice battered veteran Bo Cantrell enough to win by technical knockout.
Since then, Slice has fought once -- a first-round knockout in February of Huntington Beach native Tank Abbott. With each bone-crushing right hand, his fan base grew.
"He's got the 'it' factor," Smith said. "Who cares who Kimbo's fighting, Kimbo is worth watching."
At 6 feet 2 and 240 pounds, Slice said he's not concerned with his opponents either.
"That'd be me stepping out of my mental boundaries that I'd normally be in to prepare for a fight," he said. "I just kind of stay focused and look at it like it's another mountain to climb, another hurdle to jump."
Before stepping into the cage, Slice worked as a bodyguard for a strip club, then doubled as a limousine driver and one-man security team for an adult-film company. In his spare time, he started beating other men into submission, usually in the backyard of a residence, the back parking lot of a boatyard, or anyplace out of view of local authorities.
The fights were posted on the Internet, where he quickly built a worldwide audience.
"I was literally fighting for respect in the streets," he said.
Slice remembers getting into his first street fight when he was 13, but can't pinpoint when it became a hobby.
He recalls watching Clint Eastwood play the character of Philo Beddoe in "Every Which Way But Loose," a late-1970s film about an easygoing trucker who roams the San Fernando Valley looking to pad his income by fighting anyone who dared raise their fists.
"When guys, literally, starting betting on it, it was an opportunity, in a way, for me to make some extra cash," Slice said of his backyard fights. "I would've rather done that than to do something more far worse. You know, a street hustler or drug dealer or something. . . .
"So that was a good way for me, at that time, to do what I had to do."
In his entire fighting career, Slice has lost once. That came in 2004 against Boston police officer Sean Gannon. Slice bloodied Gannon's face but was knocked down three times in the 10-minute brawl, finally succumbing to fatigue.
Gannon landed a UFC fight a few months later but has since been prohibited by the department from moonlighting as an MMA fighter. However, insiders believe a rematch could be in the works later this year, one way or another.
If that occurs, it could be one of the most popular fights in MMA history. By then, Slice may even need a bodyguard.
MIXED MARTIAL ARTS
Kimbo Slice vs. James Thompson
Tonight at Newark, N.J.
9, Ch. 2