A rainbow coming out of SpongeBob’s hands is one of the many memes the cartoon has sparked. (Knowyourmeme.com)

Tom Kenny never thought SpongeBob SquarePants, a character he originated on the children’s program almost 20 years ago, would one day end up on Broadway. Why would he have? Parents clamp their hands over their ears whenever they hear SpongeBob’s helium voice, let alone his nasal laugh. The anthropomorphized sponge is no Hugh Jackman.

And yet, “SpongeBob SquarePants: The Broadway Musical” is up for 12 Tonys on Sunday, tied with “Mean Girls” for the most nominations. Its resonance with serious theatergoers is surprising until you consider that even as adults, those of us who watched the series can’t shake its omnipresent songs, references and memes. Somehow, it became a cultural earworm.

At 25, Ethan Slater, who plays the character in the musical, can’t imagine a life without “SpongeBob.”

“It doesn’t seem like anything that was ever new,” he said. “It’s sort of a silly comparison, but I’ve likened SpongeBob to the Greek gods, these hegemonic characters who everybody knows. Nobody is going to see a picture of SpongeBob and ask who it is.”

The same goes for Slater’s performance in the stage production, which director Tina Landau ensured would emulate the Stephen Hillenburg-created TV character’s most prominent qualities. SpongeBob is still a silly guy who lives in a pineapple under the sea and who, with his dolt of a best friend, Patrick Star, bothers their curmudgeonly neighbor Squidward Tentacles. Bikini Bottom is still an inexplicably psychedelic setting for the creatures’ antics. Their singsong-y outpouring of nonsense will still get stuck in your head, although this time it’s actually music.

Ethan Slater, front, leads the cast of “SpongeBob SquarePants: The Broadway Musical,” which features songs by the likes of John Legend, Steven Tyler and Cyndi Lauper and has been nominated for 12 Tony Awards. (Joan Marcus)

Tori Mueller, a self-proclaimed Z-list Twitter celebrity behind the popular fan account Fred MyLeg, said the musical captures the quirkiness of the show’s first three seasons, those most popular among young millennials. The 23-year-old remembers watching “SpongeBob” after school in the first grade, munching on popcorn as the sponge flipped Krabby Patties. Bits of dialogue like “I was born with glass bones and paper skin” cemented in her mind, an experience shared by her eventual high school classmate Peter Marshall, now 25. The two have tweeted out quotes and accompanying images since 2011 from a once-“grass-roots Twitter account,” as Marshall described it, that now boasts around 210,000 followers.

“Sometimes people ask, ‘how do you remember it all?’ ” Mueller said. “Cartoons are very singsong-y, and that’s for a reason. It sticks with you if you have that creative musical brain.”

This cartoon also happens to include characters so meme-able they’ve dominated the Internet for years. Ryan Milner, author of “The World Made Meme,” said he has never witnessed a single pop culture text pop up in as many different ways as “SpongeBob” has in the decade he has studied the wacky Web.

The mainstream memery began innocently, with a widely circulated image of SpongeBob smiling as a rainbow came out of his hands; you can almost hear him go, “Imaginaaation.”

But the humor quickly changed. A blurred image of Mr. Krabs is how some people on social media express deep confusion. Others announce their controversial preferences and start fights by placing an image from real life (say, pineapple pizza) over SpongeBob’s workplace, the Krusty Krab, and another (plain pizza) over its chaotic evil rival, the Chum Bucket. An image of a devious-looking Patrick gives everyone an excuse to caption it with similarly “devious” things — such as, Me leaving the pot in the sink because it needs to soak” — under the guise of celebrating our favorite Nickelodeon cartoon.

Kenny, 55, said his favorite meme — “I know about SpongeBob memes! What do you think? I’ve got kids” — is the one in which SpongeBob imitates a chicken. The sponge bawks alongside a two-part caption: an questionable statement from one person, and the mocking repetition of it CaPiTaLiZeD lIkE tHiS and attributed to someone else.

Me: Wow, this meme will never die.

Someone who loves it: WoW, tHiS mEmE wIlL nEvEr DiE.

“These poses, these facial expressions — it’s a paintbox that people use to make paintings of their own and give it new meanings and jokes,” Kenny said. “A joke spawned a joke, [which] spawned another joke. Like an amoeba splitting and resplitting. To me, that’s beautiful.”

Milner points to the characters’ archetypal nature and the show’s 19 years (and counting) of source material as reasons for this phenomenon. An image of Squidward’s grumpy face can capture anything from intense irritation to a bad case of the Monday blues. Others, such as SpongeBob, appeal to the nonsensicality of everyday life.

This absurdity mirrors that of the show, which even attracts some adult viewers — such as Barack Obama, who told the crowd at a Michigan rally in 2016 that “SpongeBob” was his favorite cartoon of the ones Malia and Sasha forced him to watch. Mueller likened the show’s humor to dadaism, because “it’s obscure and anything can happen at any time.” Is SpongeBob an actual sea creature or a misplaced dish-cleaning tool? Why is Mr. Krabs’s daughter a whale? Wouldn’t SpongeBob’s fruity abode float in water?

And does that ridiculousness translate onstage?

Of course it does, you barnacleheads. To be fair, Kenny had reservations before seeing the musical in Chicago, where it premiered in 2016. He feels like SpongeBob’s caretaker, having gotten involved in the TV show’s development so early on that the protagonist’s name was still Spongeboy. (Can you imagine?!) But his low expectations were “blown into the stratosphere” once he realized that an appreciation of his and Hillenburg’s work pervaded this new version of Bikini Bottom.

“It’s such a great realization of the characters,” Kenny said.

Danny Skinner as Patrick Star and Ethan Slater as SpongeBob, in the Broadway musical. (Joan Marcus)

Landau and collaborators managed to make the show their own, between the celebrity-written (John Legend! Steven Tyler! Cyndi Lauper!) songs and subtle costuming, as Slater dresses in a simple yellow collared shirt. Kenny had little to do with how Slater tapped into the character — “it wasn’t exactly a Luke Skywalker-Ben Kenobi situation,” he said — because he didn’t have to. Slater is “first-generation ‘SpongeBob,’ ” Kenny continued, and therefore “absorbed it subatomically through thousands of hours of watching it.”

The show, currently in its 11th season, now reaches a new generation of young viewers. In April, Kenny won his first-ever Daytime Emmy for voicing the character. He’d never been to a Broadway premiere before this, and now a song he co-wrote with Andy Paley, “The Best Day Ever,” is part of a Tony-nominated score.

All the while, Kenny continues to work on the cartoon. He recalled flipping through a recent storyboard and cracking up at the veins popping out of Squidward’s head as he drives a bus with a babbling SpongeBob onboard.

“We’re still doing new episodes every Wednesday that blow my mind,” Kenny said. “I have a house and am not living in a cardboard box under a bridge. Thanks, SpongeBob!”

Read more:

I knew little about ‘SpongeBob SquarePants’ when I went to the new musical version. It was a handicap.