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

Cassandra: Do those expensive shoes come with a name?
Lex: Lex Luthor.
Cassandra: Huh. Of Luthor... Everything Incorporated?
Lex: More or less.

Clark: She saw it.
Nurse: Saw what?
Clark: Her future.