Michael Rosenbaum returns to Smallville for its finale. As seen here, he reprises the role of Lex Luthor.
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Lux Luthor will return for the final episode of Smallville. The character is played by Michael Rosenbaum.
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A picture of Michael Rosenbaum as Lex Luthor on Smallville. He was a major character until season seven.
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Smallville Quotes

Lex: I don't like riddles, Doctor.
Dr. Hamilton: Then this object will make you profoundly unhappy.

I've seen some strange things in my life, but this definitely takes the cake...well, almost.

Jonathan