Tom Welling portrays Clark Kent, a young man with superhuman abilities, who tries to find his place in life after discovering he is an alien. He uses his abilities to help others in danger. Clark's problem in season one includes not being able to share his secret with anyone. He just wants to be normal. After months of scouting, Tom Welling was cast as Clark Kent. David Nutter had to convince Welling's manager that role would not hurt Welling's film career in order to be able to get Welling to read the pilot script. After reading the script, Welling was convinced to audition for the role.
Kristin Kreuk portrays Lana Lang, the girl next door. She has a "hole in her heart," because of the loss of her parents, and feels empathy for everyone. She feels connected to Clark. Gough and Millar were initially trying to find someone for the role of Clark Kent, but Kristin Kreuk was the first to be cast, after David Nutter saw an audition tape the actress and sent in. Kristin Kreuk left the series at the end of the seventh season, but will be back for five episodes in season eight as a guest star.
Michael Rosenbaum portrays Lex Luthor, a billionaire's son sent to Smallville to run the local fertilizer plant. After Clark saves his life, the two become quick friends. As the series has progressed, his friendship with Clark crumbled until the pair considered themselves enemies. The role was hard to cast, as no one could agree on who they liked for the role. Michael Rosenbaum auditioned for Lex Luthor twice. Feeling he did not take his first audition seriously, Rosenbaum outlined a two-and-a-half-page scene, indicating all the places to be funny, charismatic, or menacing. His audition went so well that everyone agreed he was "the guy". After seven seasons, Rosenbaum left the show.
Allison Mack portrays Chloe Sullivan, one of Clark's best friends. She is in love with Clark, although the feeling isn't reciprocated. Editor of the school newspaper, her journalistic curiosity—always wanting to "expose falsehoods" and "know the truth"—causes tension with her friends, especially when she is digging in Clark's past.[43] After learning about Smallville from the show's casting director, Dee Dee Bradley, Allison Mack thought about auditioning for the role of Lana Lang. Mack instead auditioned twice for the role of Chloe Sullivan. The character was created just for the series, and was intended to have an ethnic background before Mack was hired.
Sam Jones III portrays Pete Ross, another of Clark's best friends. He is the first person Clark voluntarily informs of his secret.He is in love with Chloe,which he keeps to himself because of the Clark-Lana-Chloe love triangle already taking place. Pete Ross was written out of the series at the end of season three but made a guest appearance in season seven. Jones was the last of the series regulars to be cast. Gough and Millar saw Jones four days before they began filming for the pilot.[46] In the comics, Pete Ross is Caucasian, and the producers chose to cast Jones, who is African-American, against the mythology.
Annette O'Toole portrays Martha Kent, Clark's adopted mother. She, along with her husband Jonathan, give Clark sage advice about how to cope with his growing abilities. In season five, she takes a state senate seat. This leads to a job as U.S. Senator in Washington, D.C. in season six, and the character's exit from the show. Cynthia Ettinger was originally cast as Martha Kent, but during filming everyone realized that she was not right for the role, including Ettinger. Annette O'Toole was committed to the television series The Huntress when Ettinger was filming the original pilot. Around the time the creators were looking to recast the role of Martha Kent, The Huntress was canceled, which allowed O'Toole to join the cast of Smallville. O'Toole had previously portrayed Lana Lang in Superman III.
John Schneider portrays Jonathan Kent, Clark's adopted father. He goes to great lengths to protect his son's secret. According to Schneider, Jonathan is "perfectly willing to go to jail, or worse, to protect his son." John Schneider was written out of the show on the series' 100th episode, with Jonathan dying of a heart attack the night of his election victory. Millar and Gough wanted a recognizable face for Smallville. Gough and Millar loved the idea of casting John Schneider as Jonathan Kent, because Schneider was already known as Bo Duke from The Dukes of Hazzard, which Gough saw as adding belief that he could have grown up running a farm.
Eric Johnson portrays Whitney Fordman, Lana's boyfriend, who becomes jealous of Clark and Lana's budding friendship, going so far as to haze Clark.He eventually reconciles with Clark, before joining the Marines.Whitney was written out of the show in the first season's finale, but he made cameo appearances in the season two episode "Visage", where it is revealed he died in combat overseas, and the season four episode "Façade", during a flashback to Clark's freshman year. Eric Johnson has expressed his pleasure in the way the writers handled Whitney's departure, by giving the character the exit of a hero.Johnson auditioned for the roles of Lex and Clark, before finally being cast as Whitney Fordman