SPOILER ALERT: This article reveals a MAJOR SPOILER for last night’s episode of ‘Supergirl’ entitled “Human For A Day” and unlike some outlets, we’re giving you fair warning before you proceed.

We’ve known since the pilot episode of ‘Supergirl’, that tough-as-nails DEO chief Hank Henshaw was hiding a secret, when he revealed his glowing red eyes.  But it turns out that his true self wasn’t the one that anyone saw coming!

In the comics, Hank Henshaw is Cyborg Superman, one of the replacement Supermen when the real Man of Steel died.  Henshaw has since unveiled his true colors and has become one of the most dangerous villains in the DC Universe eventually allying himself with the Red Lanterns.

It’s only natural that TV viewers that were already familiar with the comics assumed that David Harewood’s Henshaw would follow a similar story, especially since the character has been surly and menacing all along.’

But last night’s episode “Human For A Day” saw Henshaw reveal his true nature and it wasn’t that of Cyborg Superman, but rather J’Onn J’Onzz the Martian Manhunter!

It was revealed that years ago, the real Henshaw along with Kara and Alex’s father Jeremiah Danvers tracked J’Onn to a mysterious island, but that Henshaw (secretly J’Onn in disguise) was the only one to return.

Executive producer Andrew Kreisberg explained:

“It’s the secret of Supergirl: within the body of the series of Supergirl, there is a Martian Manhunter series rolling throughout it.  It’s the thing that makes us giggle the most.”

Harewood’s reveal as the Martian Manhunter was not the plan from the beginning.  As Kreisberg says, it was a set visit from DC Comics creative officer Geoff Johns that got that ball rolling: