'Little House on the Prairie' cast talk 50th anniversary, remember Michael Landon

It's hard to believe it's been 50 years since the Ingalls family made their network television debut in 1974.

"Good Morning America" caught up with cast members Melissa Gilbert (Laura), Karen Grassle (Laura's mother Caroline) and Alison Arngrim (Laura's nemesis, Nellie Oleson) to celebrate the 50th anniversary of the series and discuss its lasting legacy.

As for why generations of fans have continued to watch the show long after its 200-plus episodes across nine seasons came to an end in 1983, Grassle had a thought.

"People are finding values, comfort and a message that they long for," she said. "And I think, you know, it's just simple human decency."

Arngrim added that the show felt like a hit at the time but its staying power is "absolutely mind-blowing" to her.

"It's overwhelming, actually," Gilbert chimed in. "I'm remembering so much, and so much of my childhood and so many wonderful experiences and emotional experiences attached to all of these people."

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Among those who have left a lasting impact on Gilbert is the late Michael Landon, who not only played Ingalls patriarch Charles, a.k.a. "Pa," but also produced the series as well as directed and wrote many episodes.

"Technically he was the TV girl dad," Arngrim laughed.

Gilbert called Landon, who died in 1991 at the age of 54, "magnetic," saying he "drew me in but he also played with me right away."

"Our relationship immediately became parental," she continued. "But he treated us when he worked with us like contemporaries, not like kids."

As Gilbert's Laura was growing up from little girl to woman on the show, she was also guided by her TV mom.

Grassle, when reflecting on what Caroline -- or "Ma" -- gave Laura and, by default, those who watched the show, said she "can only think it's love."

The trio of actresses -- and other cast members -- will reunite at the "Little House on the Prairie 50th Anniversary Cast Reunion & Festival" this weekend for the three-day festival running March 22-24 in Simi Valley, California. Get more details here.

See then-and-now photos of the "Little House on the Prairie" cast members:

Melissa Gilbert (Laura Ingalls Wilder)

Karen Grassle (Caroline Ingalls, a.k.a. "Ma")

Alison Arngrim (Nellie Oleson)