‘Arthur’ is (sob) over after 25 years. The people behind the cartoon aardvark say goodbye.

Long before Arthur became a children’s television treasure, he was an aardvark with nose insecurities in a popular book series.

But in 1996, author and illustrator Marc Brown turned "Arthur" into what eventually became the longest-running animated children's TV series. With more than 200 episodes spanning 25 years on PBS, "Arthur" touched the lives of several generations, from Gen X parents who watched with their millennial children to Gen Z youngsters who can recognize traces of the show with internet memes.

The last four "Arthur" episodes aired for the first time on PBS Monday, will re-air throughout the week (6:30 a.m. EST/PST; check local listings) and be available to stream on PBS Kids. The final episode will conclude the PBS series with glimpses of the "Arthur" characters all grown up.

“Well, I knew it couldn't go on forever and ever,” says Brown, a co-executive producer for the series. “And 25 years seemed like a nice number.”

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When PBS announced last summer that Arthur Read's adventures would be ending, school-age kids weren't the only ones who went into mourning. Generations of viewers recalled their memories of the "iconic" Ziggy Marley theme song and the show's ability to gently dive into serious topics, from divorcing parents to same-sex marriage and a grandparent with memory loss.

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“It’s not fluff,” says Michael Yarmush, who was the voice of Arthur for the show's first five seasons and will return for the final episode, noting how the show taught life lessons about bullying and jealousy and instilled confidence in young viewers.

In an environment where some kids' shows aim for cheap laughs or advertising, Yarmush says, "Arthur" stood out. There's "a lot of crap" on TV, but "'Arthur' just isn't that."

Brown, 75, says shows like "I Love Lucy" and "The Mary Tyler Moore Show" helped inform his work on "Arthur," first published in 1976 and aimed at early readers, because "all the characters were just as important as the other one."

"Even though the show was called 'Arthur,' Francine's just as important. D.W. is just as important," Brown says. "We could focus a whole show on any one of these characters, and kids would get to know them better."

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The anthropomorphic "Arthur" characters were complex: School bully Binky loves ballet and classical music. Arthur's BFF Buster has divorced parents and lives with his mom. Arthur's bratty little sister D.W. wants to be included in Arthur's social life but often relies on an imaginary friend to keep her company. Francine, whose dad is a garbage man, is best friends with Muffy, who comes from a wealthy family.

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The TV version of "Arthur" also gave Brown more room to explore important topics and "deal with subjects that I couldn't deal with in a picture book necessarily but made (for) an interesting TV show," he says. In one episode, Buster explains asthma to friends by shrinking them and taking them inside his lungs. "These things that don't necessarily work as a picture book made really fun, helpful television for kids."

Brown says "Mister Rogers' Neighborhood" creator Fred Rogers, who died in 2003, was a "great teacher" and emphasized the importance of impactful television.

In a 1997 episode of "Arthur," Mister Rogers visits Arthur's school. While creating the crossover, Rogers asked Brown about one of his Arthur characters, Grandma Thora.

Brown never hinted that Thora was based on a real person in his life, so Rogers' question shocked him and brought him to tears.

“I thought, how in the heck did he know about my Grandma Thora?" Brown says. "For me as a kid, (she) was like this one person in my life, who believed that I could draw; she saved all my art in her bottom dresser drawer."

Rogers said he had a similar relationship with his Grandpa McFeely, which is also the name of the friendly Speedy Delivery mailman in “Neighborhood.”

"Then he said something that gave me chills, he said, 'Marc, every child needs just one person to believe in them to make it in the world,' " Brown said as he aimed to create Arthur characters so viewers "can relate to any character they want to."

Like Rogers, many real-life celebrities visited the world of "Arthur." The Backstreet Boys, the late “Jeopardy!” host Alex Trebek and Yo Yo Ma were just a few of the names who made animated appearances on the show. Yarmush, who recorded other animated series including "Sagwa The Chinese Siamese Cat" and "Monster Buster Club," recalls the "Oh, snap" moment when he was introduced to the famed cellist while voicing Arthur.

“Wu Tang Clan was where it was at for me,” Yarmush says. But when Yo-Yo Ma came, “my dad was like ‘No, no, no, come have a listen; here’s who’s coming to the show."

"Arthur" won't be erased from history. Reruns will be available to stream on PBS Kids, and new content like podcasts and timely video shorts will be produced beyond the final four episodes.

"I was happy about what Arthur accomplished,” Brown says. “I think in many ways, he helped us all grow up.”

This article originally appeared on USA TODAY: 'Arthur' airs final season: Marc Brown on kids show's 25-year legacy