His audition went so well that everyone agreed he was "the guy". Before Rosenbaum got the part, Martin Cummins auditioned for the role of Lex Luthor; Cummins would go on to play Dr. Garner, a neuro-scientist who experiments on Clark, in multiple episodes of "Smallville" spanning season two and three. Michael Rosenbaum is not the only actor to portray Lex on the show. There have been four other actors that have performed the role; Matthew Munn, Wayne Dalgish, Lucas Grabeel, and Connor Stanhope have all portrayed Lex Luthor as a child in various episodes throughout the series. Rosenbaum relished the opportunities he gets to show Lex's evil side, even if it is only for a few seconds in earlier seasons. Specifically, he delighted in the chance to "go overboard", like he did in "Hug" where his character pulls out a machine gun and shoots everything in sight; to the actor, this gave the audience a glimpse into who Lex was becoming. To portray Lex's signature bald head, Rosenbaum had to go through more than just a regular head shaving. Not only was his head shaved every day, but he had to undergo hours of make-up treatments on his head, in various color combinations, so that his natural hairline did not show up on film. After seven seasons of portraying Lex Luthor on "Smallville", Michael Rosenbaum decided to move on with his acting career, so he departed from the show. On February 11, 2011, Michael Ausiello reported that after the back and forth speculation as to whether Rosenbaum would return to the series, the actor finally agreed to appear in the series finale. Rosenbaum expressed that his return for the final episode was for the fans, stating, "I appreciate all of their passion, their relentlessness, and even their threats." Rosenbaum believed that Lex was trying to be a hero in season one, but that his character showed signs of having to fight "ambiguity" and stay on the straight path. The tension-filled relationship with his father, which is first established in the pilot episode, comes to a crossing in the season one finale, when Lex is left with the decision to either help his father remove the structural beam that has fallen on him, or let him die. Rosenbaum wanted the audience to see that Lex was really contemplating what his life would be like if Lionel was no longer around. As Rosenbaum explained the scene:  Season two delved deeper into Lex's darker moments, from the time he wavers to save his father's life, to his outburst at Jonathan for what he feels is unfair treatment.