<P> 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 . '' </P>
<P> 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 . '' </P>
what episode does lex luthor return in smallville
what episode does lex luthor return in smallville
the series finale
the series finale