The beginning is while the Joker wildly guns down other cars demanding Batman hit him. This line is not said in the film, but would have been placed during the scene where Gordon and Batman discuss the Joker's ferry situation. The script has Gordon yelling to Batman: "Then he'll blow them both up! There's no time- we have to go in now-" and Batman responds: "There's always a catch with him-" before getting ready to rescue the hostages from the hospital.