Natalie Abrams for ew.com
During the Invasion crossover, the heroes of Supergirl, The Flash, Arrow, and Legends teamed up to battle the Dominators. However, some fans griped that it wasn’t quite a four-way crossover because the storytelling didn’t actually take place across all four shows. Save for a brief epilogue scene during Supergirl‘s winter finale, the action was mainly featured on The Flash, _Arrow, _and Legends, making it a four-way crossover on three shows.
I was definitely critical of this when we did our review. In fact I would say it was my biggest complaint. Glad this is being corrected for next year.