Only saw the movie once, but did not the original Joker break out of jail ? You know that he at least had some type of plan.
He also made have used a backup. Call someone in the theater and ask if the coast is clear. Then when they say yes, tell them you are going for the door, if it wont open, you will have to open it. That could be the plan of a diabolical genius like the Joker, but script writing is not my forte.
creepy I was just thinking the same thing. In TDK Joker let himself get captured and had an inside helper blow the place up and help him escape.