On mirror universes and 4th D negative.

[isis]

You remember that episode where the Holodeck produced a character that could outsmart Data?
They got trapped on the Holodeck thinking they weren't in it.

you mean this one? it might be my favorite.

PICARD: Moriarty, you were conjured up to attempt to defeat Holmes here. Once that attempt is concluded, win or lose, your programme has run its course. Your existence is done.
DATA: Congratulations, Professor, I capitulate to the better man. Your victory, sir, is well earned.
MORIARTY: It's gone beyond that little game, Mister Data. And you'll note I no longer call you Holmes. Whatever I was when this began, I have grown. I am understanding more and more. And I am able to use the power at my fingertips. (big shake) I can affect this vessel, and I can inflict bodily harm on you, and on your Doctor.
PICARD: Yes, you can do that, but you haven't. I suspect you shook this ship in order to get my attention. Well now you have it. What is it you want?
MORIARTY: The same thing you want for yourself. To continue to exist. If I destroy these surroundings, this vessel, can you say it doesn't matter to you? Interesting pun, don't you agree, for matter is what I am not. The computer has taught me that I am made up only of energy.
PICARD: That may not be entirely true, Professor. This which we call the holodeck uses a principle similar to another device called a transporter. In the year in which we live, humans have discovered that energy and matter are interchangeable. In the holodeck, energy is converted to matter. Thus you have substance. But only here.
MORIARTY: And if I step off this holodeck?
PULASKI: Then, Professor, you will cease to exist.
PICARD: You are not alive. As I said before, you are only
MORIARTY: A holographic image, I know. But are you sure?
PICARD: Oh yes.
MORIARTY: Does he have life? He's a machine. But is that all he is?
PICARD: No. He is more.
MORIARTY: Exactly. Is the definition of life cogito ergo sum? I think, therefore I am.
PICARD: Yes, that is one possible definition.
MORIARTY: It is the most important one, and for me the only one that matters. You or someone asked your computer to programme a nefarious fictional character from nineteenth century London and that is how I arrived. But I am no longer that creation. I am no longer that evil character, I have changed. I am alive, and I am aware of my own consciousness.
PICARD: Moriarty, my responsibility is this vessel and its crew.
MORIARTY: I want my existence. I want it out there, just as you have yours.
PICARD: That may not be possible.
MORIARTY: Then you must murder me, Captain.
PICARD: I cannot give you what you want.
MORIARTY: Because you do not know how to convert holodeck matter into a more permanent form.
PICARD: Yes, that is so.
MORIARTY: A pity. What I have seen, what I have learned, fascinates me. I do not want to die.
PICARD: And I do not want to kill you.
MORIARTY: Madam, I have enjoyed your company. Computer, arch. Cancel override protocol. Return control of the holodeck to main computer. My fate is in your hands, as perhaps it always was.
PICARD: Bridge, this is the Captain.
RIKER [OC]: Commander Riker here, sir.
PICARD: Number One, the situation is under control.
RIKER [OC]: Aye, sir.
PICARD: Moriarty, this vessel's computer has a vast memory capacity.
MORIARTY: How well I know.
PICARD: You will not be extinguished. We will save this programme, and hopefully, in time, when we know enough, we will bring you back in a form which could leave the holodeck.
MORIARTY: Then perhaps we'll meet again some day, Madam.
PULASKI: It could be a long time. Time won't pass for you, but I may be an old woman.
MORIARTY: But I'll still fill you with crumpets, Madam. I detest long goodbyes. You have the arch.
PICARD: As you wish. A short goodbye. Computer, save the programme of the character Moriarty, and then discontinue.
(Moriarty disappears)