Lois Lane (Erica Durance) was introduced in season four of Smallville when she comes to investigate the mruder of her cousin, Chloe Sullivan. However, when she finds out Chloe is still alive, she enrolls in Smallville High to finish the high school degree she never did.
As of season seven, Lois has been a reporter for The Daily Planet. Though her and Clark often butt heads and love to tease each other, there's definitely going to be a Lois and Clark in the future. Duh, have you read the comics?
Kat (to Clark): You're the Popeye to my Olive. The Mickey to my Minnie.
Lois: The sick to my stomach.
Lois: Who the hell are you, then?
John Corben: I'm a field reporter. I spent the last few years in Afghanistan. hopefully that gave me enough training to be your desk mate.
Lois: Don't bet on it.