Arrow has had it's fair share of DC characters making special appearances on the show. The list goes on from the likes of, The Huntress, Black Canary, Solomon Grundy, Firefly, Deadshot, Deathstroke, Harley Quinn, and the Flash, who coming to the CW this fall, will be receiving his own spin-off television series.
Here is a list of characters I would like to see incorporated in [The Flash](movie:15273) TV series.
Green Lantern (Hal Jordan)
With all that being said; At the end of season 1 of [Arrow](series:720988), we received many references to Ferris Aircraft, possibly hinting at the Green Lantern. I think if the show introduced Hal and Barry as friends and than later we see Hal become the Emerald Guardian, it could be a nice start to another spinoff show, revolving around GL.