According to Fassbender, Walter is a dumbed down version of David, whose overly human characteristics began to unsettle potential buyers.
David (and Fassbender) will make a reappearance in the highly-anticipated Alien: Covenant, but this time, he won’t be the only android on board.
One of the most notable performances from Prometheus was that by Michael Fassbender, who played an android named David who begins to resent his human creators.
This difference is perhaps most apparent in the separate viral video marketing campaigns for David and Walter.
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Prometheus - Viral Video - Meet David (2012) Ridley Scott Movie HD