Is there anyone on the planet who doesn’t know who lives in a pineapple under the sea? You don’t even have to watch the animated series to know that absorbent and yellow and porous is he. Heck, you don’t even have to own a TV.

According to Nickelodeon, more than $13 billion in SpongeBob SquarePants-related consumer products have been sold since the show premiered in 1999.

Rodger Bumpass, who voices Squidward, said his own “world’s largest merchandising collection” of those Bikini Bottom treasures has taken over his house. “I’ve got a special room for it now,” he said. “I’ve got everything from food to candy to dental supplies — which, of course, follows the candy part — and models. Everything.”

Nickelodeon is celebrating the 20th anniversary of the show — TV’s No. 1 kids’ animated program for the past 17 years — with “SpongeBob’s Big Birthday Blowout” (Friday, July 12, 5 and 6 p.m., Nickelodeon). It will include a live-action segment that’s surreal, even for this series.

Tom Kenny voices SpongeBob and has appeared as Patchy the Pirate in live-action segments. But he’ll be joined for the first time by Bill Fagerbakke (the voice of Patrick Star), Carolyn Lawrence (Sandy Cheeks), the show’s writer, known as Mr. Lawrence (Sheldon Plankton and Larry the Lobster) and Clancy Brown (Mr. Krabs), all playing doppelganger versions of their characters.

It’s a tribute not just to the show and its voice actors, but to creator Stephen Hillenburg, who died due to complications of ALS in November; he was 57.

“It was really weird, and then really fun,” Carolyn Lawrence said. “Eventually, I think it became very familiar and it seemed just like a natural thing for us to do. But at first, just wearing the outfits and standing in that set was really strange.”

“Trying to actually look like your character, that was a pretty tough thing to try to do,” Bumpass said.

“Clancy couldn’t not call Rodger Squidward, even though his character’s name was something else, because he’s been calling him Squidward for 20 years,” Fagerbakke said.

(Photo courtesy of Robert Voets | Nickelodeon) The staff of the Trusty Slab in the 20th-anniversary "SpongeBob SquarePants" special — JimBob (Tom Kenny), Manager (Clancy Brown), Carol (Carol Lawrence), Robber (Mr. Lawrence), Patrick Star (Bill Fagerbakke), Manward (Roger Bumpass), Patchy (Tom Kenny).

In the hourlong episode, the residents of Bikini Bottom are planning a big surprise birthday party for SpongeBob, so Patrick takes him to the surface world to get him out of the way — and they visit a restaurant that looks suspiciously like the Krusty Krab, the restaurant where SpongeBob works.

‘The million-dollar question’

“SpongeBob” is seen in more than 200 countries and territories, translated into 55 languages and watched more more than 100 million people worldwide — according to Nickelodeon, its most widely-distributed property ever.

The network has produced a lot of really good, really successful animated shows — “Doug,” “Rugrats,” “Hey Arnold,” “CatDog,” “The Wild Thornberrys,” “Fairly OddParents” and more — but none have had the same broad, long-lasting appeal.

What made “SpongeBob” catch on and kept it popular for two decades?

“Man, that’s the million-dollar question,” Fagerbakke said. “I don’t know if there’s a formula. There’s something mercurial and enigmatic about it. And I’ve come to think it’s a magical combination of shapes, colors and sounds.”

Bumpass also pointed to the show’s animation style — bright colors and sight gags. Executive producer Vincent Waller said he thinks SpongeBob is wish fulfillment for kids.

“He has the life they want,” Waller said. “He has a job he loves. He doesn’t have parents to answer to. He lives in a house by himself. But he is still obviously a child at heart. And I think they see that, and they just go, ‘Ooh, I want that.’”

“He’s also the-glass-is-half-full all the time,” said Carolyn Lawrence. “He’s the person you want to be with that’s always looking at things from a positive angle. ... I think it’s a really fun place to go be.”

Way back in 1999, (the official series debut was July 17 of that year) my kids got an early look at “SpongeBob.” (TV critics get to preview shows. And, 20 years ago, that meant popping a tape in the VCR.) The three of them then kept bugging me about when the show would premiere so they could see more.

For 8-year-old Jonathon, it was love at first sight. “It was funny,” Jonathon remembers today. “It made me laugh.” And it was a show that I could watch with him, because I found it funny, too.

“I always feel like we’re writing a comedy show, not necessarily a kids’ show,” said the writer Mr. Lawrence (real name: Douglas Lawrence Osowski). “We’re writing a show for families to all be able to watch together, but we’re thinking of the comedy all the time.”

Besides the “physical humor,” he said, there’s always an emphasis on being witty and “visually stunning.”

“SPONGEBOB” FUN FACTS
• SpongeBob is 4 inches tall.
• SpongeBob was originally named SpongeBoy by creator Stephen Hillenburg.
• SpongeBob has failed his driving test 1,258,056 times.
• SpongeBob has been The Krusty Krab’s employee of the month 374 times.
• SpongeBob can cook Krabby Patties so quickly because he is ambidextrous.
• The recipe for Krabby Patties is a secret, but Hillenburg hinted that the burgers may be vegetarian. Otherwise, some inhabitants of Bikini Bottom would be cannibals.
• Squidward only has six legs because animators thought eight legs on the character — which would be correct for an octopus — made him look too burdened.
• SpongeBob is allergic to tulips. The Dutch named a new species of tulip after SpongeBob in 2010.
• In 2011, a new mushroom species — Spongiforma squarepantsii — was named after SpongeBob.
• Squidward was originally pink.
• “SpongeBob SquarePants” has saved lives. In 2007, a family was saved from a sinking boat by plugging up the hole with a SpongeBob football. In 2012, a Long Island girl saved her friend from choking because she learned the Heimlich from an episode of the show; and an Australian man lost at sea was found by a helicopter that spotted his yellow SpongeBob trunks.

‘SpongeBob’ spreads!

By Season 2, Fagerbakke recalled, there was a “John Lennon kind of buzz around the playground” when he “would pull up to the elementary school to pick up my daughters. ... I was kind of stunned that all those kids were so hip to it.”

Carolyn Lawrence said the kids in her neighborhood started calling her by her character’s name.

“I was recognized in my dentist’s office the other day,” Bumpass said. “I said, ‘How in the world did you know me?’”

When former President Barack Obama entered the White House in 2009, he cited “SpongeBob” as one of his favorite shows and said he watched it with his daughters. “That blew our minds,” Kenny said.

The series is a habit for a whole lot of people, and it’s continuing to find new fans with new generations of kids. “It found its way into the fabric of people’s lives, and it kept finding new life in new ways like memes and things like that,” Kenny said.

And “SpongeBob” continues to branch out. Nickelodeon has ordered a prequel series, tentatively titled “Kamp Koral,” about 10-year-old SpongeBob at summer sleep-away camp. A third movie, tentatively titled “It’s a Wonderful SpongeBob,” is scheduled for release in May 2020.

There’s no end in sight. “We want to be popular on other planets, too!” Kenny said. And, well, we can’t rule that out.