On Sept. 16, 2018, Ethan Slater braced himself for the final performance of “SpongeBob SquarePants.” The Nickelodeon musical had been open on Broadway for nine months, and it received generally positive reviews and 12 Tony Award nominations. But the Palace Theatre was closing for multiyear renovations, forcing the undersea spectacle to shutter as well.

That last audience was filled with devout fans, some who had seen the show dozens of times. Families had flown in from out of town, millennials came dressed in cartoon costumes. And before anything had really begun, they were all on their feet and cheering loudly at the entry of foley artist Mike Dobson, who performed hundreds of sound effects that animated the actors onstage.

Backstage, Slater — who portrays the porous, persistently optimistic sponge — was moved to tears.

“Even though he wasn’t visible on the Broadway stage, the foley was such a quintessential part of the show,” he recalled of Dobson, who was in the orchestra pit. “It was this perfect moment when I realized that even though we were closing, our audience had understood what we were doing. It ended up being like that for the whole show, full of these beautiful little realizations that this was the last time we were gonna perform this.”

Or so he thought. Last month, the cast and creative team reunited for “The SpongeBob Musical: Live on Stage!” which will simulcast at 7 p.m. Saturday across Nickelodeon, TeenNick and Nicktoons. The airing is part of the yearlong celebration of the 20th anniversary of “SpongeBob SquarePants,” created by the late Stephen Hillenburg.

“This is something that deserves a wider audience, so we absolutely wanted to film it in whatever way we could,” said Rob Bagshaw, Nickelodeon’s executive vice president of unscripted and live events. “‘SpongeBob’ has always been at the forefront of many of our tentpole characters, and the fact that it’s an existing title made it obvious for our first project. We love the results, and we’d like to do more.”

Like the many entries into the “live musical event” space — whether airing on network television or broadcast to movie theaters through National Theatre Live — the upcoming “SpongeBob Musical” aims to make theater accessible to a new audience.

“Even though our show always had affordable options when it was on Broadway, if you live in Kansas, a $35 ticket to the show also comes with a round-trip plane ticket,” Slater said. “As a young person who didn’t grow up in New York, this would’ve meant a lot to me. I hope this will inspire a new generation of theatergoers, who aren’t close to Broadway, to check out regional productions or tours.”

Nickelodeon’s presentation less resembles the offerings from NBC, Fox and ABC than those from PBS, Netflix and BroadwayHD. “The SpongeBob Musical” will be captured and edited for an airing rather than broadcast live. Most of these pretaped titles do not air — or, sometimes, are not even announced — until after the original stage show has closed, possibly as a cautionary move to not cannibalize ticket sales.

Recently, that unofficial rule was broken when Netflix announced that Mike Birbiglia’s one-man Broadway show “The New One” would premiere on the streaming platform in a month’s time. Netflix made the announcement just before the tour began its month-long stop at Center Theatre Group’s Ahmanson Theatre in Los Angeles. CTG producing director Douglas C. Baker didn’t think the Netflix news negatively affected ticket sales.

“If anything, it raised the profile of the production and brought us the attention of a lot of people who wouldn’t have otherwise known about us,” he said in a statement. “We are working in a crowded entertainment market, so any opportunity to introduce new audiences to the theater is priceless. Hopefully we hooked them on the live theater experience and will be seeing them back at Center Theatre Group for future productions.”V

But if TV audiences nationwide can watch “The SpongeBob Musical” from the comfort of home and through a service for which they already have paid, will they buy tickets to the touring version of the Broadway show, now on the road and coming to the Dolby Theatre in L.A. in the spring?

Pantages’ general manager, Jeff Loeb, whose company is bringing “SpongeBob” to the Dolby, is throwing his full support behind the airing.

“We have seen our fans enthusiastically engage on social media whenever a musical is aired on television, and for fans of musical theater, seeing the show once and only once is never enough,” he said in a statement. “Being able to see a live capture performance on television or in a movie theater gives fans additional opportunities to enjoy the art form they love. It is also a great way for patrons who may not have been able to travel to Broadway to see the show prior to seeing it locally at the Dolby Theatre. Live broadcasts are a win-win for everyone.”

Bagshaw said that Nickelodeon supports both endeavors equally and that the airing might encourage viewers to buy tickets to the “SpongeBob” tour. Tina Landau — who directed the show on Broadway, on tour and on-screen with seasoned awards show helmer Glenn Weiss — is OK with the concurrency, as long as the show is being seen in some way.

“For me, this show was, and continues to be, a vessel of joy and hope and optimism,” Landau said. “It has been nothing but a gift that we all want to give and share with audiences, and however we do that works for me.”

What “The SpongeBob Musical” does have going for it over network television’s other live musical events is the luxury of time. This is the taping of a production that was created over a decade, and it features most of the entire original cast, who spent years developing their characters and played them for Broadway audiences eight times a week for nine months. They bring the brand’s beloved cartoon characters to life without wearing the theme-park bodysuits.

Slater, who perfected his personification of SpongeBob over six years, spends the entire show dressed in a gingham yellow shirt, skinny red tie and brown plaid pants. He evokes SpongeBob through a high-pitched, nasal voice and a zippy head-to-toe physicality. He even added some new bits for the taping — an extra backflip here, a riskier trick fall there.

“Ethan had some incredible moves and facial expressions that we really took advantage of with a close-up, to accentuate moments and really bring it home on TV,” said Weiss, who directed the telecast. “It’s like the cartoon, which you’re not watching from a faraway seat. It always zooms in on his eyes, so we wanted to do that too.”

During the two-day shoot at the Theatre Royal Plymouth in England, Weiss and Landau worked together to capture as many design elements as possible: the intricate ensemble formations in “(Just a) Simple Sponge.” The apocalyptic lighting design in “No Control.” The invaluable work of foley artist Dobson, now primely positioned in a visible corner of David Zinn’s vibrant, Tony-winning scenic design.

To make the show work for a television schedule, Landau and book writer Kyle Jarrow had to identify spots for commercial breaks and trim the script by about 15 minutes. The latter was a tougher task, because every song is composed by a different songwriter — among them David Bowie, Sara Bareilles, John Legend, Yolanda Adams, and Steven Tyler and Joe Perry of Aerosmith.

“I always felt like the Broadway version was too long, but I didn’t know how to get those minutes before we opened,” Landau said. “I was so happy with how we ended up doing it because rather than cutting any whole songs, we did small nips and tucks and somehow got it down for the time. Coming back to this with a little distance, it was like, ‘We don’t need that favorite joke of mine.’”

With 20 years of brand recognition on its side, “The SpongeBob Musical” sets the sincere simplicities of the series to song. SpongeBob belts out about his dream to manage the Krusty Krab; its greedy owner, Mr. Krabs (Brian Ray Norris), wails of his love of money. The pessimism of Squidward (Gavin Lee) manifests in a spectacular tap-dance number that uses his numerous tentacles and comes complete with a clarinet solo. And starfish Patrick (Danny Skinner) wonders, with all his might, what words rhyme with “rock.”

Instead of being based on any particular episode, “The SpongeBob Musical” features an original story line: A fatal volcano eruption is on the horizon, invoking sheer pandemonium among the residents of Bikini Bottom. Science-minded squirrel Sandy (Christina Sajous) calls it a symptom of “tidal warming.” She’s scapegoated as an outsider and told to go back where she came from. A dictator-like mayor eggs it all on.

The musical has become all too prescient, noted Landau.

“From the beginning, the story was always about the end of the world and how approaching danger can turn a society or a community in on itself,” she said. “That just became more a mirror of what seems to be happening in the world, as time went on. It was interesting how increasingly political and timely it became without our ever working towards that as a goal.”

According to Slater, its applicability is what makes it so fit for a television broadcast. “Unfortunately, the themes of xenophobia and climate disaster are always relevant,” he said. “But there’s a broader consciousness and a larger discussion about these things now, so it’s a great time for it to be on TV and reach a wider audience.”