"Crisis on Infinite Earths" is a crossover event in the Arrowverse, a shared universe of superhero television series. It aired in late 2019 and early 2020, spanning five episodes across various shows, including Arrow, The Flash, Supergirl, Legends of Tomorrow, and Batwoman. The storyline revolves around the multiverse facing destruction from an entity known as the Anti-Monitor, prompting heroes from different Earths to unite and save their worlds. The event features numerous characters from the DC Comics universe, including Oliver Queen (Green Arrow), Barry Allen (The Flash), and Kara Danvers (Supergirl). It explores themes of sacrifice, heroism, and the interconnectedness of different realities. The crossover received positive reviews for its ambitious scope and nostalgic references to past DC adaptations.