What weapon does the Joker use in The Lego Batman Movie?

The Joker uses Superman's Phantom Zone Projector in The Lego Batman Movie. The device can send people into the Phantom Zone, a prison dimension containing some of the most dangerous villains in the LEGO universe.

Batman initially steals the projector from the Fortress of Solitude because he wants to defeat the Joker permanently. He sends the Joker into the Phantom Zone, but this turns out to be exactly what the Joker wanted. Harley Quinn later steals the projector from police custody and uses it to bring the Joker back.

Once free, the Joker releases a large group of villains from the Phantom Zone, including major threats from across the LEGO universe. Their escape allows him to launch a coordinated attack on Gotham City and gives the film its central large-scale conflict.

The Phantom Zone Projector is easy to confuse with the Joker's usual chemical weapons, such as laughing gas or Smilex. Those are associated with other Batman stories, but they are not the key weapon in this film. Here, the projector matters because it turns the Joker's defeat into the mechanism of his return.