yup yup! it's the red kryptonite episode!!! makes him eeeevil!!!
RED( Episode 4)
In this episode Red Kryptonite plays an important role. Red Kryptonite has an effect on Clark which turns him evil. His libido is also heightened by the Red Kryptonite as he is after more girls then just Lana...which makes lana jealous!
one of his lines: "i never knew how easy it would be to get what i want."
if you want more details, check out the smallville spoilers i posted a couple of weeks ago. they are on page 2 of this forum.