Spoilers for last night's "Supergirl" — specifically the reveal at the end of it — coming up just as soon as I learn what it feels like to break a bone...

The title story of "Human For a Day" did its job in terms of showing Kara what it's like to be powerless, and demonstrating that she'd be heroic even if she couldn't fly or lift a car over her head. Still, the episode's big development was about a different alien, who's been playing at being human for much longer than a day.

(Serious comic book nerd stuff ahead, so if you'd rather not know how the various Berlanti shows relate to the comics, read no further.)

In the comics, Hank Henshaw was introduced as an analogue of Reed Richards from the Fantastic Four, but quickly turned into one of Superman's biggest villains of the last few decades: the Cyborg Superman (sometimes merely called Cyborg) who would destroy an entire city and do lots of other monstrous things. When the TV show chose that name for David Harewood's character, everyone who knows the comics assumed he'd eventually become the Cyborg, and once we saw Hank's eyes glow red, some of us assumed he had already been so transformed.

Instead, this turned out to be an excellent — and more rare than it should be — case of one of the DC shows turning the hardcore fans' knowledge against them, with the revelation that Hank isn't a cyborg at all, or even Hank Henshaw, but a new alter ego for one of the founding members of the Justice League, J'onn J'onzz, aka the Martian Manhunter.

This was the smarter way to go. "The Flash" already done the whole "the team leader is really the big bad" bit, so making Hank into the villain would have felt like a rehash. And J'onn is not only a great character, but one who can help Kara deal with the idea of being an alien walking among humans, having virtually no one from her home world left (though, between her cousin and her evil aunt, she's got more survivors around than he does), and someone who can pitch in whenever Aunt Astra's plan kicks in, so that we won't be as quick to wonder why Superman hasn't also showed up to stop a full-scale alien invasion. And because he's a shapeshifter, the series doesn't have to feature him in his natural, very big and green form too often, though the effects work during his brief appearance last night looked pretty good.

Also, I think there are times when the other DC shows have leaned a bit too much on very specific versions of the characters from the comics, when one of the advantages of having 70-odd years of stories (depending on the character) to draw from is that you can keep people guessing about what's going to happen next. Felicity on "Arrow" has almost nothing in common from that character's original comics incarnation, and that show's been better for her prominence than if the series had tried to force an Oliver/Laurel relationship because Black Canary has a long written history of dating Green Arrow. Just because the characters, particularly the supporting ones, share names with people from the comics doesn't mean they have to be exactly the same. Hank Henshaw is a perfectly acceptable substitute secret identity for Martian Manhunter, who in the comics has tended to pose as a human detective named John Jones. (John Ostrander's great '90s Martian Manhunter series revealed that J'onn actually had many guises that he adopted around the world, a device I wish other writers had continued, though it's an easier thing to do in a solo book, and he's usually just a Justice League member.)

What did everybody think of the reveal? Were you disappointed that we won't see Supergirl battling the Cyborg down the line, or excited that the series slipped a classic DC hero into the main cast while we weren't looking?

Alan Sepinwall has been reviewing television since the mid-'90s, first for Tony Soprano's hometown paper, The Star-Ledger, and now for HitFix. His new book, "TV (The Book)" about the 100 greatest shows of all time, is available now. He can be reached at sepinwall@hitfix.com