“The Polka King” is one of those titles you scroll by because you’re sure you’ve seen it, even if you haven’t.

It stars Jack Black as a loveable, generous but criminal con artist, a real person who used other people’s money to “make music, bring joy.” Change the accent from Polish to Texas and drop the polka band and it’s a lot like “Bernie,” without the whole murder and cover-up thing.

There was a well-traveled documentary based on the guy, Jan Lewan. And the trailer to this movie tells so much of the story and its colorful characters it can make you think you caught this comedy when Netflix unleashed it back in 2018.

Well, that’s my excuse anyway. I was as shocked as anybody that I hadn’t gotten around to it.

Black, co-stars Jenny Slate, Jason Schwartzman and a seriously wound-up Jacki Weaver make this guy worth rooting for even if the can’t-miss movie does miss, here and there, as it covers some fairly predictable ground. It bubbles to life even as it is never quite achieving liftoff.

The story dates from 1990s Pennsylvania, with Polish Jan (Black), ex-beauty queen American wife Marla (Slate) and Jan’s first original musical collaborator Mickey (Schwartzman) telling their back story to one of the legions of little old ladies and gents who packed Elk Lodges and Sons of Poland halls all over blue collar America to hear The Polka King and his band.

Jan is the biggest cheerleader for the “land of opportunity,” where “nothing happen without you believe!”

Jan believes. But pragmatic Mickey hears from his fixed-income/tightwad elderly relatives the crux of the band’s problem. Their trapped-in-time audience won’t pay for a ticket that will cover their expenses.

“Band too big,” “booking fees, too small.”

They can sell merchandise at shows and Jan can peddle Polish nostalgia at a strip mall gift shop that Marla runs. But Jan is delivering pizzas to and the like to make ends meet. And his increasingly shrill mother-in-law (Weaver) is barking “get realistic, get a stable job.”

Jan figures his “25 year plan” to “build empire” doesn’t allow for that kind of concession, and Marla is in his thrall and can’t see “writing on wall.”

But a solution might be to get their fans to “invest” in Jan, the band and his “empire.” He offers “promissory notes” to such backers, promising a whopping 12 percent return. He gets enough backers that he’s able to pay the band, beef up the show and deliver spectacular entertainment at senior citizen’s prices.

He’s delusional, of course, buying air time for DIY TV commercials, setting up his own polka record label and dreaming of the day “we get TV show, like ‘Sonny & Cher.'”

Of course it all depends on friends getting other friends to invest. It’s a Ponzi scheme, something pointed out to Jan by the Pennsylvania SEC investigator (JB Smoove) assigned to his case.

“No worry, I stop. I no know!” is all it takes for Jan to reboot the enterprise, to add “Jan Lewan Tours of Europe” and a pierogi shop to his portfolio.

“In Poland, everybody do bribes,” he queries the SEC guy. “You do bribes?”

No, he doesn’t. But that doesn’t mean Jan won’t resort to that to pave the way for getting rich and famous, making others dreams come true and getting his tour group “audience with the (then Polish) Pope.”

“Polka King” is a movie with the occasional giddy high — that “Pope” moment — a few predictably touchy and even more predictably touching scenes, and a lot of pleasantly goofy polka music by this America-loving, gregarious and generous goof who just wants to take care of people — his family, his fans, and his employees.

Schwartzman underplays his voice-of-practicality partner in crime — who is actually in the dark on these chained and padlocked filing cabinets and Jan’s mysterious “books.” Slate’s Marla is equally delusional, craving identity and generally more passive and less interesting than you’d figure a role written for Jenny Slate would be.

But Weaver, as the “I always KNEW something was up” raging, mistrusting mother-in-law, brings the heat and the laughs to her testy turn.

It’s Black’s movie, and his polished stage-mugging is used to great effect, just as his general likability will have you rooting for this not-quite-victimless-crime and the open-hearted, if devious, criminal behind it.

How Jan kept all those “investors” happy has to be one of the great books-juggling acts this side of Bernie Madoff. His secret, as Black suggests in every scene, might have been his charm.

You meet Jan Lewan and you ask him, “Is it pronounced ‘Yan’ or ‘JAN?'”

“Whichever you want,” he replies. And when you insist, he insists. He’s that eager to please, to fit in, to “be just like you.”

The film’s striving immigrant subtext kind of overwhelms the knowledge that somewhere down the line, a lot of people are going bust over this guy’s hustle. When Black’s Jan says he’s doing it because “I play the polka music for the smiles,” you believe it because he believes it.

And even when shoe drops and the music’s over, you can’t help but root for the lovable, grammar-mangling, old-lady-fleecing mug.

Rating: TV-14

Cast: Jack Black, Jenny Slate, Jacki Weaver, Jason Schwartzman, Vanessa Bayer and JB Smoove.

Credits: Directed by Maya Forbes, scripted by Maya Forbes and Wallace Wolodarsky. A Netflix release.

Running time: 1:35