When Oliver, Barry of Earth-1 and Supergirl of Earth-38 (the heroes of their respective shows) face off against their evil counterparts from Earth-X

and Earth-1 (in Barry's case with his opposite being the Earth-1 Reverse Flash)

Overgirl scoffs at the ridiculousness of Oliver aiming an arrow at her.

She is understandably quite shocked (as is Supergirl for that matter) when it turns out to be an arrow made out of kryptonite.

Oliver answers Kara's question as to why he has it:

"In case an evil you ever showed up!"

When she showed up during the previous crossover, Kara had been mind-controlled, so it is not a bad idea to have a contingency plan in place in case something like that happened again.

He doesn't say anything as to how he has it, though.

My question therefore is:

How did Oliver Queen of Earth-1

  • learn of the existence of kryptonite in the first place, and of the fact that it is harmful to Kryptonians (something that by the pilot episode of Supergirl Kara herself didn't know [although it has become an Earth-38 idiom for crippling weakness within 2 years! (iirc Lena asks Kara what her Kryptonite is at some point)])
  • procure enough of it to craft an arrowhead. As far as we know there are no Kryptonians on Earth-1, therefore debris from Krypton should not have been dragged across the galaxy (or galaxies depending on where Krypton is in this continuity) to crash there. We know from Supergirl - 3x04 - The Faithful that Krypton-38 did send probes with soil samples to other worlds, so maybe Krypton-1 did that, too?

Edit: I just noticed that I'm apparently not the only one to ask that question.

  • My guess would be that one of the Wells was actually more responsible.
    – phantom42
    Commented Feb 13, 2018 at 15:09
  • 1
    I think he got it from Bruce Wayne. Because Bruce Wayne and Gotham city have been mentioned in both universes (Earth-38 and Earth-1). And all Batmen have contingencies. Oliver of Earth-1 knows Bruce so its highly probable that Bruce gave him the kryptonite or told him how to synthetically manufacture one.
    – Shreedhar
    Commented Feb 13, 2018 at 15:35
  • @Shreedhar Batman certainly exists on Earth-38 (when James mentions people seeing his Guardian armor with fear, as they do "Clark's friend" Winn actually uses his fingers to mime bat ears) and Bruce Wayne certainly exists on Earth-1 (Oliver mentions him by name in Arrow 6x02), but even if Oliver got the kryptonite from Earth-1 Bruce, the question would be the same: How could Earth-1 Bruce know about it, its properties and how could he procure it? We don't know if there's Earth-1-Batman. If there was I think with all the vigilante discussions in city council he would have been brought up.
    – BMWurm
    Commented Feb 13, 2018 at 15:42
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    Since Flash and Arrow are in the same universe, and Arrow is friends with Team Flash and knows Kara is from another Earth, maybe he just calls up Cisco one day: "Cisco, buddy, ol' pal, mind doing me a favor? I want to be prepared in case an evil Kara ever shows up. Can you breach over to Kara's Earth, vibe what can hurt her, and bring me back a sample? Thanks" Commented Feb 13, 2018 at 16:29
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    It was established that there are Kryptonians throughout the multiverse, not just in Earth-38's universe. Oliver could have asked Cisco if he knew about something that could affect Kryptonians, and between Cisco's girlfriend being a multiversal traveler, and Cisco working with Harry who also knows much about the Multiverse, they might have discovered the evidence concerning kryptonite and acquired some for Oliver. Commented Feb 14, 2018 at 5:04

1 Answer 1


Is there kryptonite in Earth-1 universe?

In Legends of Tomorrow, Rip Hunter says this

I've seen men of steel die and dark knights fall

Those are direct references to Superman and Batman. Which means they must exist in some capacity on Earth-1 (Since Rip Hunter is from Earth-1). Given that, we can infer that kryptonite exists in the Earth-1 multiverse.

Where did Oliver obtain kryptonite?

That's a more challenging question (since it isn't directly addressed), but in this capacity we see Oliver kind of taking on the role of Batman in Tower of Babel, in that he is developing contingency plans for super heroes in case they go bad.

From an interview with Stephen Amell:

“I think Oliver has definitely researched Kryptonite, for sure. Like Kryptonite, and how do I take away his super-speed? I might need to waste these guys at some point, and I’m going to have my bag of tricks.” - Heroic Hollywood

He could have used Cisco to either vibe details of Supergirl (and her weaknesses) from across the multiverse, or more directly used Cisco to travel to Earth-38 to try and acquire some. I'm more partial to the first one, given knowledge of kryptonite they could have searched for it on their own Earth (since it presumably exists somewhere in their universe).

  • Rip is a time traveller, therefore Superman might exist at a future time (the past is unlikely or Barry would have recognised the S when he arrived on Earth-38 by accident for the first time): otherwise I would have expected him to make an appearance when a nuclear missile destroyed a small town and hundreds more were started a few days later, or when Aliens invaded his Earth, or when 2 alternate versions of his cousin appeared and battled each other over a church. But if he is from a future time, now kryptonite has not yet likely been dumped on Earth-1.
    – BMWurm
    Commented Oct 5, 2018 at 7:36

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