Supergirl is crammed full of comic book references, and unlike Man of Steel, the show wastes no time in introducing Kryptonite. It first appears when the young hero is shot out of the sky by Department of Extranormal Operations goons sent in by Hank Henshaw. If that name is familiar, it's because he's better known as Cyborg Superman in the comics. There's not so much as a reference in the pilot to him transforming into that character though. It is however clear that he's not a fan of Kara suiting up and fighting crime. Kryptonite then reappears when it's used to handcuff Supergirl to a table, and it's clearly the first time she's been exposed to the radioactive remains of her home planet. It doesn't have any sort of visual effect on her though, and doesn't really seem all that deadly. Whether or not it will end up playing a larger role in the story moving forwards isn't made clear.
