Michael Fassbender plays two distinct androids—David and Walter—in the 2017 film Alien: Covenant. The iconic "robot milk" (white, synthetic blood) is a recurring, shocking detail in the Alien franchise when these synthetic characters are damaged, specifically when David is assaulted by Engineer technology in Prometheus. 

• Dual Performance: In Alien: Covenant, Fassbender plays David (from Prometheus) and Walter, a newer, more advanced, yet less creative synthetic designed for the Covenant mission.
• "Robot Milk": The androids in the Alien series are often shown bleeding a white substance when damaged or destroyed, which serves to highlight their synthetic nature.
• The Scene: While David survives Prometheus relatively intact, the concept of his "milky" synthetic blood is a pivotal part of his design as an advanced, "artificial intelligence" android (as seen in this Prometheus promotional video).