They actually play the scene well, the Trickster is quietly observing a the amassed villains that Neron (who is, essentially, Satan) has gathered, and sees the "High Council" of bad guys who are there to endorse Neron. He sees Luthor, and Circe and Doctor Polaris.. and is impressed.. then sees that the Joker is there and is instantly "Oh shiiiiiiiiit!".