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Walter Rothchild is mentioned twice in the second to last story of the book WWR Illustrated Number One. In this story of Nom de Plume and the Dirty Deeds Squad, he is credited to running the Rothchild Corporation and described as "a loony who sits up on the moon making robots."
This description of Walter Rothchild is inconsistent with the design of Darwin Rothchild as mentioned in WWR Illustrated Number Two, where he is also credited with running the Rothchild Corporation.
It is unknown whether or not Darwin Rothchild and Walter Rothchild are the same person or two different characters in the WWR Universe; or whether or not this inconsistency is intentional.