As you can see, he is real


You can clearly see him fighting Anasui after beating him once before (thats why its the final round

To unlock saul, you must do a few things.
First you must complete all of all star mode (this step is not optional!)

Second you must have a law degree and ask the developers to give you a hidden steam key (activation code) for the character. They will ask you for your law degree. you must have a law degree from the correspondence course from the University of American Samoa.

If you are not American any high school diploma will do.

Finally, once you have your key you will not instantly have him unlocked. In order to unlock him you must first beat all characters in the arcade on maximum difficulty.

After that you should get a special cutscene saying; you called? my name is saul goodman and you unlocked me.