In the Sapienza map, the player can find two men dressed in outfits marked as "Green Plumber" and "Red Plumber", which seems to be a reference to Mario and Luigi.
Contributed by Psychospacecow
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In the Bangkok level, there's an NPC who mimics then presidential candidate Donald Trump and references quotes like “I could make my country great again!” in the same blusterous mannerisms.
Contributed by KnowledgeBase