"Sin Tzu" is a play on the name of Sun Tzu, writer of "The Art of War". Likewise, all of Sin Tzu's defining characteristics (his philosophical mentality, his obsession with war and strategy) are also derived from the historical figure.
In one cut-scene, Batman sees Poison Ivy, Mr. Freeze, Harley Quinn and the Joker imprisoned in Arkham Asylum. These were the four primary villains of the last major Batman video game "Batman: Vengeance". Also, as he passes each one, the BGM tracks from the villains' individual settings (or levels) can be heard.