Oct. 14, 2010 -- A massive descendant from the Ice Age locks its horns under a fence, and lifts.
With a toss of its head, the outdoor pen is heaved off the ground. A relentlessly barking dog dances around the monster, careful to sidestep its lethal weight. Noise and energy kick up with the dust when the enclosure soon threatens to collapse. A riptide swirls as a roar drowns the tumult in its own deafening thunder.
"Hello, Wildthing! Hi baby!" Sherron Bridges says as the shaggy head of the buffalo swings past the kitchen doorframe only minutes later.
Deadly horns are inches from her chest as Wildthing walks by, sniffing the air and gently inspecting treasured family heirlooms and furniture. Sherron, along with her husband RC, invites their pet buffalo named "Wildthing" inside the house whenever he wants human companionship. Incredibly, it was her idea.
"Why not? You let your kids into the house, don't you?" says Sherron.
"[Wildthing] loves coming in. I have to make him leave and then he comes back in if the door is open," says RC. "The house used to look bigger before he grew."
It's a safe bet that no one had this in mind when they first sang about a home where the buffalo roam. But likely no one ever thought they'd see a buffalo serving as the best man in a cowboy's wedding either.
"Well, he just sat up there lookin' all nice and pretty. And he held the rings and when he got tired of holdin' 'em, he slung 'em off," Sherron recalls.
"He's actually been real good for our marriage. It's really kept it interesting," RC adds.
Wildthing, technically a bison, has lived with Sherron and RC Bridges in Quinlan, Texas, for the last five years. He's a beloved and frankly startling member of their family.
"I don't think about him bein' dangerous. To me he's just a little baby," says RC.
They began raising Wildthing when he was a calf on the verge of death. His mother couldn't nurse him properly, so RC jumped in with a bottle and soon fell in love with the little bison's fiery spirit. Now six feet tall, and a very healthy 2,100 pounds later, Wildthing and RC have an unshakeable bond.
"He is my best friend. He just melts with love," says RC.
CLICK HERE to see photos of Wildthing
RC Puts Life on Line With Giant Bison
It is a relationship built on extraordinary confidence -- perhaps, even some blind faith.
"These guys are well over a ton," says Dave Salmoni, a large animal expert for the television network Animal Planet. "They can run about 35 miles per hour, which is faster than a horse. And you picture that coming at you, it's like a small car but worse, because this has horns."
Salmoni, who has worked with bison at Yellowstone National Park, where they have attacked and injured twice as many people as grizzly bears over the years, came with ABC News' "20/20" to meet Wildthing for insight -- and for our protection.
"Bison react aggressively to things that they are scared of," Salmoni says. "That just means you've got a humongous animal with horns and knows how to use him. He's going to start throwing you around."
But RC, 61, doesn't avoid taking this bull by the horns. He has spent his entire career as a rancher and rodeo clown, learning the crucial skills of how to handle fear and to roll with the punches. And there have been many over the decades.
"When I was 14 years old, a horse knocked my teeth out. I've had a huge amount of broken ribs and broken shoulders. I had my neck broke twice, and never missed a day's work," says RC.
Few others would choose to risk even more serious injury by living with a horned relic from the dinosaur age. Yet, RC never has shied away from being close to Wildthing. In the scorching heat of a Texas summer, the unlikely pair can be found swimming together in a nearby pond.
Wildthing Leaves Wildness at Welcome Mat
So how exactly did RC befriend the largest land animal in North America?
"I got him bluffed," he says. "And that's all there is to it. He's just bluffed. He doesn't attack me for two reasons. He thinks I'm tougher than he is, probably. But the bigger reason is that he loves me."
Love may just be the ace in the hole. Somehow, Wildthing knows to leave his wildness at the welcome mat.
"He's never been bad inside here," RC says. "Tears up everything outside and doesn't tear up anything in the house. One time, he picked up a couch and moved it. I told my wife she probably had it in the wrong place anyway! I would rather have him be in here than my kid most of the time."
Wildthing may be a well-behaved bull in a china shop, but RC knows that raising a bison as part of the family takes a special breed of human.
"Don't take a day off. It's seven days a week and it's three or four times a day," says RC. "I've never tried to make him a super gentle animal cause I enjoy him being wild. I want him safe for me, and I sure don't want him hurting anybody else. But I enjoy his wildness."
RC has enjoyed crossing nature's divide. And there is no returning after a lifetime of extraordinary and seemingly impossible feats.
"Matter of fact, I may be nuts and it may be exactly why I'm doing this!" says RC. "It's strange in your world, but it's not strange in mine 'cause I've lived with animals for 40 years."
Woman Considers Rodent Part of the Family
When it comes to outrageous family members, Melanie Typaldos of Buda, Texas, understands that love comes in many sizes and species. She is the proud owner of Caplin, an unlikely entrant on the giant spectrum.
Caplin weighs more than 100 pounds, which may not seem noteworthy compared to a 2,100-pound bison, but is enormous when you hear what he is: a capybara.
"Capibaras are the world's largest rodents," says Typaldos.
CLICK HERE to see photos of Caplin
The top-recorded capybara weight is more than 230 pounds; a rodent that weighs as much as a man.
Capybaras are native to South America, which is where Typaldos first saw the super-sized cousin of the guinea pig on a family vacation. She found a breeder in the States and brought Caplin home when he was 11 days old.
"When I saw him, I just fell in love immediately," says Typaldos. "He sleeps with me every night. When the weather is cool, he likes to get under the covers. He doesn't snore."
And like Wildthing, Caplin has a gentleman's manners in the house.
"He's housebroken. Capybaras like to go to the bathroom in the water. So we just have a bowl of water that's in the bathroom right next to the toilet," says Typaldos.
As for diet, capybaras eat plants, leaves and grass. His teeth are long and razor-sharp, which Typaldos learned from painful experience. She is quick to point out that prospective owners should think very carefully before considering a capybara for a pet.
"He took out about a quarter-sized piece of flesh, even though I was wearing jeans and he bit me through the seam of the jeans," she says. "His teeth are very sharp, and I really worried about that. But I wasn't willing to give up on him so easily."
Raising Capybaras as Companions
There are almost no guides for raising capybaras as companions. Typaldos discovered the best way to deal with the growing pains was just to give Caplin his space.
"The thing with the capybara is, you cannot win in a case of dominance," she says.
So he's a little bit like a benevolent despot with a huge following: On land, where he never fails to turn heads, and online with a surprising number of Twitter followers.
"He has about 3,500" followers, says Typaldos. "He's very rodent-friendly. He's a big promoter of wildlife issues. He tries to be very educational and very cute."
Cute is in the eye of the beholder. If you fancy rodents, they don't get any bigger than a capybara. If 2,100 pounds of swinging horns is more your style, there is always Wildthing.
And if there is one thing Caplin and Wildthing have in common, it's that the humans who love them may be even wilder than they are. As a young cowboy, RC never anticipated that one day he'd be sharing his television remote control with a buffalo. (Wildthing prefers the cartoon "SpongeBob Squarepants").
"I probably wouldn't have believed you," laughs RC. "But if you told me that was really gonna happen for sure, I would have eaten it up."
Watch the full story on a special edition of "20/20" Friday at 9 p.m. ET.
For even more on R.C. and Wildthing's extraordinary relationship, watch Animal Planet's series "Fatal Attractions."