In Justice League Unlimited, there's a running plot where the Justice League and a shadowy US federal department called Project Cadmus which is led by Amanda Waller start butting heads with each other. The situation gets really tense when someone remotely controls the Justice League's space-based Watchtower and fires the tower's fusion cannon on an abandoned Project Cadmus base. After Waller orders a response against the Justice League, Batman drops in for a visit which consists of this scene:
Here, Batman refers to three people who are smart enough to remotely control the fusion cannon in order to fire it. While the third person he alludes to is clearly Lex Luthor, Batman mentions that the other two people were already on the Watchtower. Who are these two people?