While promoting his new movie 'Teenage Mutant Ninja Turtles: Out of the Shadows,' Stephen Amell - the actor who first gained fame starring as Oliver Queen in the CW's 'Arrow' - was asked if he knew of any plans involving a crossover between his series and 'Supergirl.' He responded, "I think that it?s highly likely that, if you have four DC superhero properties on one network, that that is an opportunity that might not ever exist again, and certainly hasn?t ever existed in the history of television. So I expect them to do something."