Michael Fassbender pulls double duty in his new film Alien: Covenant. Not only does he reprise his role as David, the uncanny android who really messes things up in Prometheus, but he also portrays Walter, a new and improved version of the former. We sat down with Michael (and director Ridley Scott) to get the details on how he managed those scenes with himself and mastered those two instruments. Hint: it involves a lot of careful choreography . . . and some slapping.