Critics panned it. Fans skewered it. Ratings were middling. But in the end it didn’t really matter what anyone thought about Lifetime’s “The Unauthorized Saved by the Bell Story” when it ran over Labor Day weekend last year. It did the job.

“We ended up getting a 47 percent new audience that had not been to Lifetime,” said Tanya Lopez, that network’s senior vice president for original movies. And the average viewer age dipped into the 30s, which was unheard-of at Lifetime.

“So all around, the network was thrilled,” she said. “And we thought, ‘Did we catch lightning in a bottle or should we try it again?’”

They are trying it again.

This Saturday, Lifetime will introduce “The Unauthorized Full House Story.” In October, “Beverly Hills 90210” and “Melrose Place” will receive similar treatments. For Lifetime, it’s part of an attempt to solve the problem that faces all networks in today’s fractured viewing world: How do you bring in new audiences?

Lifetime is trying to tack away from the “women in peril” movies that it was once known for. After several years of original scripted shows like “Army Wives” and “Drop Dead Diva,” the network scored one of the summer’s most well-reviewed new series, “UnReal.” Its “Unauthorized” movies are part of its attempt to expand viewership and skew younger by tapping nostalgia.

Lifetime, a cable network, is not alone in that, of course. Nostalgia, specifically for TV shows from the late 1980s and early ’90s, is at a fever pitch. “Fuller House,” a spinoff of the ABC sitcom about a widower raising three daughters with help from his brother-in-law and best friend, will have its debut on Netflix next year. A reboot of the sitcom “Coach” is moving forward at NBC, Showtime is bringing back “Twin Peaks” and Fox’s short-run sequel to the “X-Files” will begin in January.

Lopez said that the “Unauthorized” franchise is in line with Lifetime’s mission to reimagine its brand as “premium, popular and diverse.” “This falls into the popular bucket by bringing in the audience that is engaged in the pop-culture zeitgeist,” she said. “That is a bigger play for us to get a younger audience.”

The inspiration for the franchise came after the network’s version of “Flowers in the Attic,” based on the 1979 V.C. Andrews thriller and its 1987 film adaptation, performed above expectations. Six million people watched the movie, which had its premiere in January 2014, a number that made it one of the most watched TV movies in years.

The buzz made executives think: “What was nostalgic? What felt good?” Lopez said. “And ‘Saved by the Bell’ came up.”

The network was uncertain how audiences would react to the announcement, but the Internet “blew up” with speculations about who would be cast and what stories would be told, she recalled, especially since the movie would be partly based on a tell-all memoir by the cast member Dustin Diamond, who played the ever-awkward nerd Screech.

And despite the fact that the term “unauthorized” is loaded with the potential for delicious scandal, Lifetime was reluctant (for philosophical and legal reasons) to excavate unverifiable rumors, however juicy. Instead, it is touting the movies as love letters to the series, devoid of mean-spiritedness and embarrassment to the actors and creators. That hesitance might be why there were so many bad notices: One “Unauthorized Saved by the Bell” review used the phrase “impotent dramatic tension” and another wondered why “there was so very little to hold our attention.”

“There was never any talk about getting down and dirty with it,” said Ron McGee, who wrote screenplays for unauthorized versions of “Saved by the Bell” and “Full House.” “In fact, there were times when I would try to lean toward the drama, and Lifetime execs were like: ‘Can we really validate that? Are we sure that’s true, or is that just a rumor someone was airing?’”

When writing the screenplays, McGee drew on episodes from the series and anecdotes, found in period magazines like Teen Beat and online interviews, about how the shows were cast, how the actors interacted on-set and any friction in their offscreen lives. In the case of “Saved by the Bell,” the result was a straightforward coming-of-age tale about actors growing up in front of the camera. With “Full House,” it was “the idea that this was the happiest set in Hollywood but that real life was a lot harder,” he said.

The drama and controversy surrounding “Beverly Hills 90210” and “Melrose Place” was well documented in the tabloid press, Lopez said, and the network won’t shy away from presenting that in those “Unauthorized” movies.

In “The Unauthorized Full House Story,” viewers will learn why Bob Saget, who starred in the original show as the corny-but-loving father Danny Tanner, traded blue stand-up for family comedy; the intricacies of Dave Coulier’s love life; and how that phenomenon known as the Olsen twins came to be.

They’ll also watch Justin Gaston, a former underwear model and onetime boyfriend of Miley Cyrus, channel the essence of John Stamos in a voluminous wig and black tank top. Not that Gaston, who like Stamos is a guitarist and gets to strum a few chords on screen, had to do much more than read his lines and look good.

“I tried to listen to some interviews and emulate him to a certain degree,” he said. “But there was actually only about a week between getting this role and going to film. There wasn’t a lot I could do.”

It remains to be seen whether viewers actually tune in for “The Unauthorized Full House” in greater numbers than they did for “Saved by the Bell.” Allowing people to revisit the thing they loved as a younger person can have the opposite effect.

“I think we sometimes tend to conflate nostalgia with actual excellence,” said Maris Kreizman, author of the forthcoming book “Slaughterhouse 90210,” which pairs quotes from works of classic literature with screen shots from popular television series. “I think that’s what a lot of this ‘Full House’ stuff is. Upon revisiting it, it’s kind of sad and depressing. I watched a couple of episodes recently, and it was a bad show that I loved very much, and that was OK for that time of my life.”