Strange thing, this Natitude.

Over the course of 81 home games this season, the rites, rituals and codes at Nationals Park have become both passionate and arcane. We finally let Teddy win. We never asked clown questions. And when Washington Nationals outfielder Michael Morse approached the plate, we threw our lungs into the least-macho battle cry in all of Major League Baseball: A-ha’s “Take On Me.”

More than 41,000 fans will help sing the ’80s mega-hit on Wednesday afternoon when the Nats host the St. Louis Cardinals in Game 3 of the National League Division Series. You remember the words, right? “Take on me . . .” A little bit louder now: “Take me on . . . ” Then, the music vanishes from the loudspeakers and the fans finish the chorus in banshee falsetto: “I’ll be gone . . . In a day or twooooooo!” (Does anyone really know that last line, though? Inay-oh-oooooooooh!)

This is all news to the guys in A-ha.

“That’s fantastic!” says A-ha guitarist-keyboardist Magne Furuholmen in an e-mail sent from his home in Oslo. “This song has done the rounds, but I never heard of it engaging the audience in this way.” Furuholmen adds that he’s ready to switch his allegiance from the Red Sox to the Nats.

And let’s be real. When Red Sox fans croon Neil Diamond’s “Sweet Caroline” during the eighth inning at Fenway Park, it gives us only another reason to hate the Red Sox. “Take On Me” has all the giddy charm of “Sweet Caroline,” but doesn’t feel half as hokey. It’s much trickier — hence, more fun — to sing. Oh, you don’t think it strikes fear into opponents’ hearts? Listen again. What’s more terrifying than a soprano mob belting out an Aqua Net-doused feel-good anthem while its team is burying yours?

Morse steps into the batter’s box to “Take On Me” only late in the game, when stakes are high. Compared with the songs his teammates have chosen for some of their at-bats — Bryce Harper likes the effervescing synthesizers of Bassnectar’s “Vava Voom,” Danny Espinosa digs Kanye West’s “Mercy” — “Take On Me” is decidedly old-school.

Morse was only 3 years old when the song topped the U.S. singles chart on Oct. 19, 1985. It’s still the hit that A-ha is best remembered for, even though the Norwegian pop trio went on to sell 36 million albums before a farewell world tour in 2010. In 1991, the group performed in awe as an audience of 198,000 sang along to “Take On Me” during a concert at Rio de Janiero’s Maracana Stadium. And it still pops up in plenty of other unexpected places.

“We have come across the song in all parts of the world and in all kinds of weird circumstances,” Furuholmen says. “From Buddhist temples in Nepal to supermarkets in Brazil.”

“True,” says A-ha lead singer Morten Harket, e-mailing from a solo video shoot in Berlin. “Anything from black metal covers to Kanye West dancing to it on stage at the Roskilde festival to a quintet of accordion players from North Korea.”

If the Nationals make it to the World Series, would the band consider popping up in Washington to perform it?

“Of course,” Harket says.

That’s even more reason to sing yourself hoarse in the wake of the Nationals 12-4 shellacking in St. Louis on Monday. We want this season to end with a World Series victory in a few weeks, not inay-oh-oooooooooh.