Since then, characters from that first season have left the series, with new main characters having been both written in and out of the series.
The season four cast—(clockwise from left) Allison Mack, John Glover, Erica Durance, Jensen Ackles, Annette O'Toole, John Schneider, Michael Rosenbaum, Tom Welling and Kristin Kreuk—contains the characters who have been on the series the longest, with the exception of Ackles who left after one season.
Smallville is an American television series developed by writer/producers Alfred Gough and Miles Millar, and was initially broadcast by The WB.
Since then, only two characters from the first season have remained regulars through to the eighth season, with seven new actors taking on lead roles from seasons two through eight.
Four of those new actors began as recurring guests in their first seasonal appearance, but were given top billing the following season.
Additionally, the series chronicles Lex Luthor's path to the dark side, and his metamorphosis from Clark's best friend to greatest enemy.
Smallville depicts the relationship between Clark and his first love interest, Lana Lang, as well as his relationship with Lois Lane, the woman he ultimately marries in the comic books.