Digger Harkness / Captain Boomerang is one of the most popular members of The Flash's Rogues Gallery… and he's also one of the members of the Suicide Squad which is part of the Arrow series which is where he's going to make his debut.
And the casting director on Arrow seems to love former Spartacus stars – Manu Bennett (Slade Wilson), Cynthia Addai-Robinson (Amanda Waller) and Katrina Law (Nyssa Raatko al Ghul) – so it's not surprising that they've gone to the well once more to get Nick Tarabay.
Tarabay is best known for his role as Ashur, a former gladiator who was injured and began working as an informant. He also had roles in Star Trek: Into Darkness and Burn Notice.
Harkness is scheduled to appear in episode seven and eight of Arrow with episode eight being the crossover with the Flash.