Months into an expedition through the Amazon in the early ’90s, the Kratt Brothers — as Chris and Martin Kratt are known — were on the lookout for giant river otters, German shepherd-sized animals also known as “lobos de rio,” or “wolves of the river.” A sudden snorting sound had tipped them off to the presence of the endangered predators feisty enough to chase off jaguars, so they hopped into their little boat, video camera in hand.

“We were so into it, and they were just right there,” recounts Martin. “We were getting great stuff. Then suddenly, Chris and I realized our feet were getting wet. We were so excited [that we didn’t realize] we were both on the same side of the pontoon boat … and we were already going down.”

They scrambled to protect their video equipment in a waterproof bag as the boat plunged into the river, where the brothers soon found themselves face-to-face with several giant otters. “They were coming right up to us, snorting and spraying their spray in our face… [the boat] went down and we were just floating there,” he continues. “So we got really up close and personal with them.”

That footage became part of “Kratts’ Creatures,” the educational children’s wildlife show that premiered on June 3, 1996, and kicked off over two decades of “creature adventuring,” as the brothers call it.

The Kratts’ signature style is likely familiar to anyone who has tuned into PBS over the last 25 years for “Kratts’ Creatures” or “Zoboomafoo” or the animated “Wild Kratts”: a torrent of animals facts, muddy pratfalls (or “Kratt-falls” in their parlance), and unbridled enthusiasm for learning about wildlife in a particularly hands-on manner. To see Martin engage in an elephant dung “snowball fight” in Africa or Chris laughingly get a face full of raw fish guts as he feeds a young alligator is to understand the brothers’ charm. Perpetually clad in cargo shorts, Chris always wears green shirts while Martin dons blue so kids can tell them apart. (Even in a Zoom interview for this story, the brothers remain committed to the Kratts Sartorial Code.)

But the public television mainstays, now beloved by children across several generations, were once not quite so understood by grown-ups.

Chris and Martin Kratt grew up in the suburbs of New Jersey, seeking out garter snakes and box turtles in piles of lawn clippings, and watching “Wild Kingdom” and solemnly-voiced nature specials on TV.

“At the time in the late ‘80s, there were no kids’ wildlife shows,” says Martin. “There were nature documentaries that families would watch together, but nothing made just for kids. So we thought, ‘Wow, if we could do a show that shared the adventure with kids and get kids introduced to all these amazing animals, maybe that could have some kind of impact on saving endangered species.’”

So they set about making their own nature documentaries. After graduating from Duke University with a degree in zoology, Martin worked as a research assistant to the Duke Primate Center’s Dr. Kenneth Glander on a howler monkey project in Costa Rica, then for Dr. Patricia Wright at her field station in Madagascar, then for Dr. John Terborgh in the Peruvian Amazon.

Chris, three years younger, was studying biology at Carleton College at the time and would join in on the excursions. While on those trips between 1989 to 1992, equipped with a video camera and a bootstrapped budget partly funded by grants, the brothers hitchhiked and took ox carts through the regions, saving on money by camping out in tents and surviving on peanuts and rice as they sought to film animals in the wild. (Their parents, who nervously thought their sons’ efforts were “kind of crazy,” says Chris, were nonetheless supportive.)

The Kratt brothers then edited VHS tapes and took them to elementary schools up and down the Eastern seaboard, using their enthusiastic audience as a focus group of sorts. But when shopping around their demo at networks, TV execs waved off the Kratt Brothers as “too frivolous” and said things like, “Oh, it’s really cute. Maybe it’ll be a home video, but never a television show,” they recall.

Leo Eaton, then vice president of production at Maryland Public Television, was persuaded otherwise in 1993 by a short demo featuring Chris and Martin dressed up like ponies, trying to join a herd of real-life Chincoteagues.

“I used to get dozens of tapes, so I didn’t even have time to look at it,” says Eaton. “I figured it was just a kids’ show. But my son was four years old at the time. I said, ‘Come on, Alex, take a look.’ And he must have watched that little demo 70 times. He just loved it. And I got so sick of him saying how wonderful it was — I figured I must meet these guys.”

That led to Maryland Public TV funding the production of a pilot that would go on to win best children’s film at the Jackson Hole Wildlife Festival, prompting a meeting with PBS’ head of children’s programming at the time, Alice Cahn. Eaton and the brothers expected a series order of a handful of episodes. PBS wanted 50. (Eaton would go on to executive produce the brothers’ first three series over the course of the next decade.)

The next two years of filming across Australia, Africa, the Caribbean and North America resulted in “Kratts’ Creatures,” featuring Chris grooming baby chimpanzees, Martin gnawing logs alongside beavers, and of course, plenty of pratfalls into exotic waters. “Whether kids will find the herky-jerky, hip-hop editing of ‘Kratts’ Creatures’ riveting or distracting is any grown-up’s guess,” read a 1996 Baltimore Sun story ahead of the premiere. The series would be “best served by just a touch less silliness,” said the Chicago Tribune at the time.

But those elements made it an instant hit. “When it aired in June, we went on a little tour to zoos, and we acted out an adventure on a stage. And that’s when the the kids started coming out,” says Martin. “We were very surprised by it, but it was very similar to meeting the kids in the schools that we’d done in the past.”

The show resonated with the littlest of viewers as well, leading to the development of a preschool concept at PBS a couple years later. “Zoboomafoo” was a beast of a production — literally and figuratively — combining filming of three live lemurs, a puppet lemur (brought to life by puppeteer Gord Robertson), claymation, segments featuring kids, segments featuring live animals, and field packages of the brothers in various far-flung locales.

“A few production managers at the beginning, during the planning phase, quit because they didn’t think it could be done,” recalls Chris. “Logistically, they didn’t think it could be done, because we had this puppet lemur that was going to sometimes be the real lemur and we were going to cut back and forth between them … It freaked out a lot of seasoned television professionals.”

A feat of engineering, a replica of the main set piece of Animal Junction in Canada had to be rebuilt at the Duke Primate Center down in North Carolina one sweltering September, in order to film a trio of endangered sifaka lemurs — Jovian, Nigel and Flavia — that would collectively be known as the titular character.

“Fortunately, lemurs kind of look like puppets in the first place, so the idea of cutting between the puppet version and the real live version worked in the end,” laughs Chris. “And the set of Animal Junction was very colorful and kind of confusing, so it was very forgiving if we were cutting from one place in Animal Junction to another.”

In Toronto, the primary set hosted all sorts of live animals, from elephants to bear cubs to crocodiles, with storylines adjusted to match whatever the creatures felt like doing.

“Everything was to the animals’ schedule,” says Cheryl Knapp, the Kratts’ longtime series producer who has been working with the brothers since the start of their TV career. “We didn’t ask them to do anything. We basically put them in this environment, and just watched them and filmed what they did, and then worked the story around what they did. There was no stress for them. It was a very, very, very comfortable setting for the wildlife.”

But in the middle of filming the first season, “Zoboomafoo” encountered an existential crisis. The show’s Canadian production partner Paragon Entertainment hit financial troubles, recalls Eaton, leaving a set full of crew and animals — and future of the Kratts — in limbo. After a tense few days, PBS ultimately decided to take over the production, allowing the series to live on.

By the late ‘90s, the Kratt brothers had ascended to the status of public television hotshots, with live tours drawing thousands of kids and their parents.

“It was like they were rock stars,” recalls Knapp of one enormous event at the Brookfield Zoo outside of Chicago. “And the thing is, they were just so kind. What you see is what you get [with them], especially with kids. They never rushed the kid; even now with the [‘Wild Kratts’] live show, they will take as much time as they need to talk to the kid and sign autographs.”

Parents, too, had become quite accustomed to seeing Chris and Martin’s faces on their screens. A New York Times profile from 2000 notes that “many of the mothers [spent] their line-standing time debating the relative cuteness of the two brothers.”

“The ‘yummy mummies,’” chuckles Knapp at the memory of some of the mail they would receive. “There was a fan letter from this woman, and she was saying, ‘I was looking at Martin’s big blue eyes.’ And so we’d [rib] Martin and say ‘Where’s your eyes, Martin? Where’s your eyes?’ … We wanted to hear from the kids, not from the mothers.”

So what was it like to be PBS heartthrobs?

“Zoboo is the real star here,” Chris good-naturedly deflects, quickly pivoting to the show’s ratings. “What we are really proud about is the term ‘co-viewing’ in TV, where parents watch the shows with their kids. All of our series have always had really high co-viewing.”

The wholesome Kratts, now in their 50s with children of their own, have always been more interested in promoting conservation than becoming celebs with groupies, it seems. “The guys are not that kind of thing,” says Knapp. “It wouldn’t even [occur] in their brains there.” Instead, she recalls the countless times the brothers have helped kids cultivate a love of nature, and all the times parents have thanked them for it.

“Having worked on so many different types of programming in my life, this is something that working on shows like this, and still having fun doing it, makes all worthwhile,” she says.

After filming “Zoboomafoo” for several years, Chris and Martin began itching to leave the confines of a TV studio. “We wanted to get back to being out, living with the animals for big chunks of time, because we’d spent a lot the time in Animal Junction for many years,” says Martin. So they embarked on more adult fare with “Be the Creature” for NatGeo, in which the brothers would live out in the wild with grizzlies and lions for weeks and weeks at a time, compressing around 75 hours of raw footage per trip into 40-minute episodes.

While it may be one of their lesser known endeavors — scarcely anywhere to be streamed, the first season of the show is on DVD and the second was never properly distributed — Eaton says Season 1 of “Be the Creature” is “some of the best things they’ve done.”

A production trip to the Kodiak peninsula in Alaska showed Eaton firsthand the Kratts’ extensive knowledge of wildlife, when a large bear started chasing a juvenile too close to the production for comfort. The Kratts quickly bunched up to make themselves appear bigger and disincentivize the brown bears from approaching.

“You know the old joke about, if a bear chases you, you don’t have to run faster than the bear, you only have to run faster than the guy beside you?” says Eaton, who has been on a few expeditions with the brothers. “Well, because Chris and Martin were always in front of the camera, I always knew I was safe, because there was always a Kratt between me and the bear.” (Knapp mostly opts out of the field adventures — “it’s like traveling with a men’s hockey team,” she jokes — in favor of shepherding the productions from afar, coordinating with local rangers to ensure that Ugandan trees are fruiting at just the right time to attract chimpanzees, and so forth.)

Still, after spending even a month with African wild dogs for an episode of the NatGeo series, the Kratts weren’t able to get all the footage they needed. “We had our open-air truck, and in just trying to follow them when they went off on the hunt, I think we ended up with dozens of flat tires. [We were] stuck in the sand and mud, like, five times,” says Chris. “The technology, our vehicle, couldn’t keep up with these amazingly mobile predators we were trying to follow.”

Adds Martin: “We knew there were facts about them that we just couldn’t show. So we started thinking, ‘Wow, with animation, anything we want to show, we can — any ‘wow’ fact, any interesting behavior.”

Thus “Wild Kratts” was ultimately born in 2011, their longest-running series so far, with its catchy theme song from Pure West, composers who have also been working with the brothers since the “Kratts’ Creatures” days. Each of the more than 150 episodes are bookended by live animals (and live Kratts), but centers on their animated counterparts and a tech-savvy team as they learn about and replicate the incredible “creature powers” of beavers, Komodo dragons, wolf hawks, you name it. Chris and Martin trade off drafting the scripts for each episode before working with a team of storyboard artists and animation directors to bring each story to screen.

Season 7 of “Wild Kratts” is officially in the works, though the COVID-19 pandemic is keeping the Kratts’ live-theater tour on pause until early 2022. The uncertainty of the virus’ spread has curtailed international exploration for the moment; the brothers, who live in Ottawa, Ontario, have more North American trips planned for the time being. They’re also working on a “Wild Kratts” feature film and an autobiography.

For all their goofiness on screen, the Kratts are serious about conservation, founding the Kratt Brothers Creature Hero Foundation and establishing refuges to protect wildlife habitats. The first, Grizzly Gulch, spans early 1,700 acres on the Rocky Mountain Front where grizzly bears, elk, wolves and other creatures roam. A fundraising campaign is underway for a second “creaturefuge,” with the location to be determined — with input from their fans, of course.

“Having been on for 25 years, I think one of the things that I’m most proud of is the impact it’s had on kids watching our shows, and seeing kids actually get so excited about animals and nature that they want to go on their own creature adventures in their spare time,” says Chris. “Or people [saying,] ‘Thanks for your show. Now we actually go on creature adventures as a family.’”