During a recent interview with The Hollywood Reporter, Arrow executive producer Marc Guggenheim threw some cold water on fan hopes that Coast City test pilot Hal Jordan could show up on the series, suggesting that the character is likely tied up with the planned Green Lantern film instead.

"They announced the Green Lantern Corps movie, and I’d be surprised if it didn’t include Hal Jordan," said Guggenheim, who last year lost Deadshot to the Suicide Squad film. "It would be great but I doubt it very much."

At the end of Season Three of Arrow, the Oliver seen in flashbacks was en route to Coast City, the home of Green Lantern, his rogues and supporting cast. Even in flashbacks, we've seen a number of DC heroes and villains pop up, so it wouldn't be entirely surprising to see some familiar faces appear in Coast City, especially if some of them might then resonate into the present day storyline (as happened with Deathstroke and Katana, for instance).

Arrowverse references to a disappeared test pilot (made in the "Rogue Air" episode of The Flash) might be a little harder to explain away -- but that could just as easily be just a wink and a nod to something that won't impact Arrow and The Flash directly.

Arrow returns October 7 at 8 p.m. ET/PT on The CW.