'Rugrats' Turns 25: Creators Klasky and Csupo Share Story Behind the Iconic Cartoon

— -- “A baby’s gotta do what a baby’s gotta do!”

It’s been 25 years since Tommy, Chuckie, Phil and Lil stole our hearts in “Rugrats,” the Nicktoon that hilariously featured babies who could talk.

ABC News chatted with creators Arlene Klasky and Gabor Csupo about the lovable series.

With its 15-year run on Nickelodeon, a spinoff, three films, video games, comics and toys, it’s safe to say that “Rugrats” was a 1990s force to be reckoned with.

“We had no idea that it was going to get that big,” Klasky told ABC News. “I would pick up the phones, and it would be ‘Rugrats’ fans, kids. It was pretty wild. I was here at the studio when we’d get calls and lots of letters, but every place I would go, we’d get this older group, the ’90s kids, who would start to say things like, ‘You were my childhood.’”

Before the “birth” of Tommy Pickles, she married one of the other driving forces behind “Rugrats,” Csupo, a Hungarian animator, writer and director who got her involved in character animation, she said.

Csupo came to the U.S. in 1979 and worked for the Hanna-Barbera cartoon studio after meeting Klasky in Stockholm.

In 1982 the two formed Klasky Csupo Inc. in their two-bedroom apartment in Hollywood before moving the next year to a larger office.

Years later, they became involved in notable projects — including the “Simpsons” shorts for “The Tracey Ullman Show,” shorts for “Sesame Street” and the opening titles for “In Living Color.”

“We had kind of cornered the market on opening on graphic titles, so [“In Living Color”] was one of the first ones that our studio did, and it looked pretty awesome,” Klasky said, laughing. “We both had artistic tastes that were very offbeat and forward-thinking. At least that was what we were going for.”

After their kids, Jarrett and Brandon, were born, Klasky took a short hiatus from work to be with the boys.

Soon, she said, her amusing little toddlers ignited a game-changing thought: “If babies could talk, what would they say?” she said. And so “Rugrats” was born.

Klasky and Csupo, along with animation writer and producer Paul Germain, transformed her idea into a show pilot, which was a hit on Nickelodeon.

“In the early stages, I think everybody wanted a bully, of course, and Tommy being a hero was the obvious choice,” she said.

As animators worked to shape the characters, it was Angelica, her cousin Tommy Pickles and Chuckie who became the show’s most iconic characters, Csupo told ABC News.

“We got Paul Germaine to help us shape it. I started to draw up some silly-looking kids, and then we started to put the whole group together,” Csupo said. “We hired the best animation directors from around the world. You only get one opportunity to premiere a show.”

Klasky and Csupo completed the initial episode, titled “Tommy’s First Birthday,” which aired on Nickelodeon Aug. 11, 1991. It was the first of 172 episodes that would be released over 15 years.

“The first episode was the most challenging because we were still shaping the tone of the show and the individuality of the characters,” Csupo said. “We started casting the voices, and that’s when we started to realize the richness of each character with the raspy voice of Chuckie or the mean, edgy voice of Angelica.”

Actress and voice-over talent Elizabeth “E.G.” Daily was brought on for the sweet, babyish voice of Tommy, and Christine Cavanaugh took on his nasally, timid best friend, Chuckie Finster — landing catchphrases like “I don’t think this is such a good idea!”

Cavanaugh died in 2014, and Klasky and Csupo said she will be remembered fondly for the unique voice of the freckle-faced redhead.

“She was just the most adoringly, kind and sweet person and totally dedicated for it,” Csupo said of his late colleague. “She immediately tapped into the character. She tried a few variations but came up with this quality of voice which we loved and obviously became iconic. You hear that voice and you can’t mistake it. It’s just charming and funny and different.”

“I don’t think she had a mean bone in her body,” Klasky said of Cavanaugh. “I think when we first heard her voice, it was an oh, my God experience. This woman can definitely show the vulnerability of Chuckie. She was wonderful, and we all miss her very much. In saying that, we also were very, very lucky to have Nancy Cartwright step in as Chuckie and do an amazing job as well."

As for Daily, Klasky said, "[Her] voice was so charming, and I think it just broke people’s hearts – both of those characters.”

Klasky and Csupo also produced three other Nickelodeon favorites: “Aaahh!!! Real Monsters,” “The Wild Thornberrys” and “Rocket Power.”

In 1998 “The Rugrats Movie” premiered in theaters, breaking the $100 million mark at the box office. Two years later, “Rugrats in Paris: The Movie” was released, followed by “Rugrats Go Wild,” which introduced the babies to the Thornberrys.

Since the end of a contract they had with Viacom, Nickelodeon’s parent company, Klasky and Csupo have been busy.

In 2007, Csupo directed the live-action fantasy film “Bridge to Terabithia.” He has several projects in the works, he said, including a Hungarian parody of “Mamma Mia!”

Klasky’s latest project, "Splaat," is a series of 150 webisodes. The main character, RoboSplaat, is based on the Klasky Csupo robot logo that appeared at the close of each “Rugrats” episode.

“Kids were blogging about it, [saying], ‘That always scared me as a kid. What were they thinking?’” Klasky said of the logo. “We’re very, very excited about ... this character who we’ve made not scary anymore.”

Fans of the “Rugrats” series can still get their fix via reruns on Nickelodeon’s programming block called the Splat.

As for their favorite Rugrats? Klasky and Csupo agreed: “You can’t choose between your kids. We love them all.”