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The enemy "Cybrid Joe" is a nod to an enemy from God Hand "Tiger Joe". Outside of having similar names, they both have identical animations and move sets. Many of the developers at Platinum Games came from Clover Studio, who made God Hand.
Contributed by Hipserious
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There's a cutscene in which Jack and Max are fighting and for a moment the game cuts to a strict black and white (with a little red) color palette. This is a reference to the game's spiritual predecessor, MadWorld.
Contributed by Hipserious