Part 2: [s4e13] The Joining:

Batman and J'onn attempt to infiltrate Wayne Industries to use its satellites to disrupt the Joining's signal.

During the invasion, even Gotham's villains—including The Joker, Penguin, Bane, and Mr. Freeze —fight alongside the GCPD to defend their city. [S4E13] The Joining: Part 2

" 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. Batman and J'onn attempt to infiltrate Wayne Industries