Lex Luthor, who is portrayed by Michael Rosenbaum, was a series regular on Smallville from the first season until the seventh.  Lex, of course, grows up to be Superman's infamous arch-nemesis.

Lex Luthor Quotes

But if you look at history the great men and women of the world have always been defined by their enemies.

Lex

Lex: Clark...do you believe a man can fly?
Clark: Sure. In a plane.
Lex: No, I'm not talking about that. I'm talking about soaring through the clouds, with nothing but air beneath you.
Clark: People can't fly, Lex.
Lex: I did. After the accident, when my heart stopped. It was the most exhilarating two minutes of my life. I flew over Smallville, and for the first time, I didn't see a dead end. I saw a new beginning. Thanks to you, I have a second chance. We have a future, Clark, and I don't want anything to stand in the way of our friendship.

Smallville Quotes

I'm not really sure what you're doing. But I'm perfectly willing to run around and frown at technology if it'll lend a hand.

Lois

With every great relationship, Lois, comes a great burden...and the strength to carry it.

Carter