Arrow co-showrunner Marc Guggenheim has been fairly vocal about the likelihood - or lack thereof - that a Green Lantern could appear on Arrow. Despite hints and Easter eggs that reference Hal Jordan and his ring-slinging alter ego, Guggenheim has maintained that managing to include the character on the show is "doubtful."
However, this morning, Guggenheim made Green Lantern fans' spider-sense tingle when he tweeted a Coast City travel advertisement which used part of the Green Lantern oath, along with the caption "Production art for Arrow season 4."
Production art for Arrow Season 4... http://t.co/uds93UmdLv— Marc Guggenheim (@mguggenheim) August 31, 2015
Of course, this doesn't mean that Green Lantern is headed to Arrow. It could be a tease, or simply another Easter egg capitalizing on Green Arrow and Green Lantern's relationship. Fans will likely find out some time this season of Arrow, which premieres October 7 on CW.