It just had to happen.

Batman gained a female counterpart in 1956 in Batwoman, just in time to head off these freaky academics who were convinced Batman and Robin were P-Town buddies.

Readers had to wait five years for the next obvious addition to the Bat-Family.

In “Bat-Girl!” in “Batman” No. 139, cover date April 1961, written by Bill Finger and drawn by Sheldon Moldoff, the Bat-Family has been cornered by those dastardly fiends, the Cobra Gang.

A ring of electricity is closing in on them.

Holy electrocution!

But wait!

Swooping in on those convenient drapes, a wisp of a girl, who looks as if she weighs 70 pounds wet, clobbers a crook and shuts off the dastardly device, freeing our Terrific Trio.

She swings her way back out, confounding our heroes – especially Boy Wonder Robin, who may have grown a bit in the moment he spent gaping at her.

Who is she? Where did she come from? Was she frightened by a red sparrow at a critical moment in her development and decide to become a crime-fighter?

And why is there a hyphen in her name? Who knows? The writers tried the same thing with Batwoman, but Bat-Woman never stuck, and yet here we are.

This is an eight-page story, and boy, did Bill Finger know how to pack in plot in those days. (Eight pages today and you might get a hello.)

Batwoman returns to her Batwoman lair and receives a chipper visitor. Her niece Bette, asking how she did, and Kathy realizes her niece knows her secret identity.

Flashbacks reveal how Bette came to stay with her aunt:

“Hi, Aunt Kathy! You once said I could visit – so here I am!”

Is that the most brash way of freeloading you’ve ever seen?

“Hey, remember that vague invitation you extended me with no real date indicated? Here’s my bag, when’s lunch?”

I love this kid.

After Bette realized her aunt is the great Batwoman, she decided to make a costume like hers.

(It’s nothing like hers. It’s more like Robin.)

Now she wants them to be a team like Batman and Robin.

Batwoman spent months getting told by Batdick that she couldn’t fight crime, so of course she’s going to be supportive of another young woman entering the field.

Kidding!

She goes to Batman for advice, and he suggests she only pretend to allow Bette to be Bat-Girl, but only after a lot of training.

That way, she can stall Bette until it’s time for her to go home – whenever that is.

(Somewhere, in some “Secret Origin” story locked away in a DC desk drawer for years, you just knew perky Bette killed her parents before visiting Gotham.)

Bette isn’t so easily fooled – or foiled – by all those endless exercises and studying. She gets a lead on the Cobra Gang and tracks them to their hideout. She figures she can distract them with a “self-inflating ballon from (her) crime compact.”

Apparently her and her aunt both shop at the same novelty shop.

That balloon is even less effective than you’d imagine, and Bat-Girl is taken hostage.

When our Bat-Family comes to the rescue, Bat-Girl makes up for it by pretending to faint and turning on her captor.

“Not bad – for a girl!” Robin says as the quartet clean house.

After the thugs have been carted away, Batwoman congratulates her niece.

“Maybe we will go out as a team some day!”

Sigh. Another vague invitation. She’s learned nothing.

Bette is no slouch – she doubles down and suggests she and Robin team for a case.

Bat-Girl did return, just two issues later, but her career was limited.

“The New Look” Batman, a realistic rendering in 1964, swept away much of the fantastical trappings of the series, including both heroines.

There was no place for whimsy, or even equal representation, much less a ground-breaking female lead and her female sidekick.

The creation of Barbara Gordon’s Batgirl, meeting the demand of producers of the popular 1960s “Batman” TV series, in “Detective Comics” No. 359 in 1967 would seem to doom the original to obscurity.

That wasn’t the case.

Both Batwoman and Bat-Girl enjoyed brief revivals in the late ’70s.

Batwoman even teamed with the new Batgirl in “Batman Family” and “Freedom Fighters,”  However, in a 1979 issue of “Detective Comics,” she was viciously and pointlessly killed off.

Editor Denny O’Neil explained, “We already had Batgirl, we didn’t need Batwoman.”

You would think the original Bat-Girl would have been the hero considered redundant.

Yet she joined Titans West, and after “Crisis on Infinite Earths,” rebranded herself as Flamebird.

To my knowledge, Bette Kane and Barbara Gordon have never met.

Considering the number of heroines who have fought crime under the name “Batgirl” in the ensuing years, including Stephanie Brown, Cassandra Cain and Helena Bertinelli, DC is missing an opportunity: Crisis of Infinite Batgirls would fly off the shelves.

Speaking of fun books, this issue is a joy even beyond the introduction of Bat-Girl. It also includes the stories “The Blue Bowman,” the new persona of Signalman and just as inept, and “The Island of 1,000 Traps,” in which the Dynamic Duo hunt a crook on an island only to find themselves hunted by the many mechanized threats there.

It’s a great issue, full of adventure, excitement and pure heroism, truly the best of the era. You don’t have to spend a fortune to get a copy. You can get it on the DC Comics app.