4. Green Arrow
While the team behind Arrow understandably want to keep that world a little more grounded than The Flash’s, the fact that this version of Barry Allen made his debut in that series will now inevitably mean that fans will be desperate to see their two worlds once again collide! Arrow is a huge success for the CW, so a crossover between the two DC comic book adaptations would be a ratings hit, regardless of whether that means that The Flash visits Starling City or The Arrow comes to Central City. Barry certainly struck up a connection with Felicty, so even an appearance or two from supporting characters like that would be fun. Marvel’s Cinematic Universe has shown just how incredible a shared world for heroes like these can be, so the teams working on both series’ would be foolish to not take advantage of that sort of dynamic on the small screen!