The Flash Confirms the Canonicity of Helen Slater's Supergirl

The Flash is yet another superhero movie that revels in multiversal mishaps, with the result being glimpses at worlds beyond the now ending DC Extended Universe. This includes cameos to various well-known DC Earths and adaptations, many of which were long rumored for the film. In fact, two superheroes in particular finally shed a light on a decades-old theory concerning continuity.