A new trailer for the upcoming Arrowverse crossover Elseworlds suggests that the Joker might be putting in an appearance as part of the event. The highly anticipated Elseworlds crossover, which will act as a midseason finale for Arrow, The Flash, and Supergirl, has already been teased as featuring classic comic book characters making their first appearances in the Arrowverse, including Elseworlds' Lois Lane and Batwoman. Now it seems the Clown Prince of Crime might be joining in the fun as well, if only in a brief cameo.
The exact specifics of Elseworlds' story have been kept a secret, but some details have been revealed by the advance trailers and posters. It's known that the chief villains will be Dr. John Deegan - an attending physician at Arkham Asylum - and a cosmic being known as The Monitor. It's also known that the Elseworlds storyline will center around reality being altered, with Barry Allen and Oliver Queen trading lives, as well as Kara Danvers being locked in a metahuman prison resembling STAR Labs' pipeline.
The Joker's existence within the Arrowverse seems to have been hinted at in a recent Elseworlds trailer, which also showed the first footage of Ruby Rose as Batwoman. At the 0:04 mark, an escape attempt at Arkham Asylum is seen (image below), with the charge through the doors being led by a pale man who jumps the guard-rails rather than using the stairs. As he does this, a mad laugh is heard under the narration, not unlike the Joker's trademark cackle in the comics.
It's worth mentioning that, much as Batman's existence in the Arrowverse has been previously hinted at, so too has reference been made to The Joker. Cisco made a reference to actor Heath Ledger playing the Joker in a post on The Chronicles of Cisco augmented reality blog. At one point, Arrow was going to introduce Harley Quinn along with the rest of Arrow's Suicide Squad, but those plans were later canned in favor of the Suicide Squad movie.
On the other hand, there are many pale-skinned, mad-villains in the DC Comics Multiverse, and the figure we see in the trailer might not necessarily be the Joker. For instance, The Trickster of Earth Three (played by Mark Hamill) was a also a pale-skinned man with a mad laugh, who sported a costume that seemed to pay tribute to both the classic Joker and The Prankster - a clownish villain who used toys and joke items to fight Superman. While there's no evidence that Mark Hamill might be making another cameo as some Elseworlds' version of the Trickster, it would be amusing if he did, especially since John Wesley Shipp is playing Barry Allen from the 1990s The Flash TV series as part of the event.
There seems little point in the trailer making this reference if it is not meant to be the Joker. Yet it also seems unlikely that, with Batman not appearing in Elseworlds, the Joker would be allowed to appear, even for a brief moment. The only certainty is that fan anticipation will continue to build as the air-date of this year's Arrowverse crossover event, Elseworlds, draws nearer.