Another key part of Team Arrow, it'd be difficult to have a crossover without John Diggle (David Ramsey) around. While he'll be one of those who has to take more of a backseat role, given the amount of heroes, he should still be important to having some fun with the Barry/Oliver switch, as evidenced by him sparing with 'Oliver' in the trailer, and it looks like he'll be getting in on the action too.
