Hank Henshaw has always seemed suspicious in CBS' "Supergirl," with all that sneaking around and eyes turning red. But his mystery has finally been solved in the penultimate episode prior to the winter break. He is not someone to be feared by sisters Kara and Alex Danvers, after all.

This week's episode of "Supergirl" had sisters Kara (Melissa Benoist) and Alex Danvers (Chyler Leigh) finally finding out Hank Henshaw's (David Harewood) real identity. After dealing with the alien Jemm, Hank tells Alex that he is really alien refugee J'onn J'onzz, saved by her father. He said he promised Jeremiah Danvers (Dean Cain) to look after his daughter, Alex and Kara. How does this bit of info change National City? A lot, says the people behind the show.

ScreenRant paid the "Supergirl" set a visit and spoke with executive produers Andrew Kresiberg and Ali Adler about having J'onn J'onzz a.k.a. Martian Manhunter in the show. Apparently, it was always the plan to have another alien refugee in the show that Kara a.k.a. Supergirl can play with. It makes perfect sense now why they never brought in her cousin Superman to help her learn the ropes.

But unlike the showrunners, Harewood didn't know from the start that he was going to be one of those lesser known DC superheroes that will matter a whole lot in Supergirl's TV universe. He was told about being Martian Manhunter two weeks from his time on the set.

Then the 50-year old actor talked about White and Green Martians in future episodes.

"The white martian species in our story is responsible for the death of the whole of the green martians. There was a fire, and they burned them. We get to see a lot of that. It's very emotional. The fans are going to be, I think, really delighted to see this, because I don't think, technically it's been able to have been done before," he shared.

Find out about what David Harewood is talking about when new "Supergirl" episodes air on CBS every Tuesday night. Final episode before winter break is on Dec. 14.