" The Joining: Part 2 " is the season finale of The Batman (2004) Season 4, originally airing on May 5, 2007. The episode concludes the high-stakes alien invasion arc and marks Batman's official transition from a solo vigilante to a member of the Justice League.
The episode ends with Batman joining J'onn on the Watchtower space station, where he meets other heroes: Green Lantern, The Flash, Hawkman, and Green Arrow . [S4E13] The Joining: Part 2
During the invasion, even Gotham's villains—including The Joker, Penguin, Bane, and Mr. Freeze —fight alongside the GCPD to defend their city. " The Joining: Part 2 " is the