"Elseworlds" Part 2 Introduces the Weapon of a Major Batman Villain

The Arrowverse's "Elseworlds" crossover traveled into Gotham City tonight, and it put some of its heroes against a Batman foe's greatest weapon.

Spoilers for tonight's episode of Arrow, "Elseworlds" Part 2, below!

The episode saw Barry Allen (Grant Gustin), Oliver Queen (Stephen Amell), and Kara Danvers (Melissa Benoist) traveling to Gotham, in hopes of finding Dr. John Deegan (Jeremy Davies) and convincing him to return reality back to normal. This brought the trio into Arkham Aslyum, where Deegan works.

The break-in into Arkham ultimately turns into chaos, as Deegan triggers an alarm and lets the patients of Arkham escape. These include Nora Fries (Cassandra Jean Amell), whose fight with Killer Frost (Danielle Panabaker) catches the attention of Oliver and Barry.

Oliver (as The Flash) arrives and tries to throw a lightning punch, but that doesn't go entirely as planned. In the process, Oliver knocks over several vials labeled "Crane", which start to emit a gas. Oliver and Barry then begin to hallucinate visions of Malcolm Merlyn (John Barrowman) and Eobard Thawne (Tom Cavanagh).

That's right -- Scarecrow's fear toxin is now canon in the Arrowverse.

For the uninitiated, Jonathan Crane is a pretty prominent villain of Batman's, who uses his experience in psychology and experimental drugs to exploit his enemies' fears. In most iterations, this manifests as a fear toxin, which has been used on a slew of DC Comics characters over the years.

Outside of the comics, fans probably know Scarecrow best from his appearances in films, TV, and such. He was played by Cillian Murphy in the Dark Knight films, Robert Englund in Injustice 2, and Arrowverse alum John Noble in the Batman: Arkham games.

It's unclear exactly what this nod to Scarecrow could mean for the Arrowverse as a whole, especially since this is the universe's first real use of the Batman side of things. But seeing as Kate Kane/Batwoman (Ruby Rose) just might be getting her own solo series on The CW, it wouldn't be impossible for Scarecrow to possibly factor in in some way, especially since it seemed like Kate had some sort of past experience with the character.

What do you think of the Scarecrow nod in "Elseworlds"? Share your thoughts with us in the comments below.

"Elseworlds" will conclude with Supergirl on December 11th at 8/7c on The CW.