Chloe and Whitney were created specifically for the show (they were never mentioned in the Superman comics). However, in 2003, DC Comics announced that Chloe would be introduced into the Superman comics.
Although he plays the lead character, Tom Welling has admitted in interviews that he is not a fan of the Superman comic books. However, Welling believed his lack of knowledge on the character mythology actually helped his portrayal of Clark.
Twin brothers Shawn Ashmore and Aaron Ashmore both appear in the show throughout the seasons. Shawn as Eric Summers in Leech (Season 1) and Asylum (Season 3), and then Aaron as Jimmy Olsen from Season 6 on.
Actors Tom Welling, Allison Mack, Michael Rosenbaum, John Schneider, and Justin Hartley are the only actors to ever appear on the show, who also directed episodes of it as well. Although they did not direct the same amount of course since Welling has directed seven episodes; Mack has directed two; and Rosenbaum, Schneider, and Hartley all directed one episode each during the show's 10 year run.
Originally, Tollin/Robbins Productions were planing to do a show that followed the story of a young Bruce Wayne before he became Batman. Since Warner Bros. Studios had decided to do Batman Begins (2005) and didn't wanted the film to compete with a television show, Tollin/Robbins Productions suggested Peter Roth, President of Warner Bros Television, to develop a show about a young Clark Kent, which later became "Smallville". The idea was later revisited and soon became Gotham (2014)
'Milo Ventimiglia (I)' originally auditioned for the role of Clark Kent. Although the role went to Tom Welling, the producers at The WB liked him so much they gave him the role of Jess on Gilmore Girls (2000). Ventimiglia went on to play a different comic book-style superhero on Heroes (2006).
The character of Tess Mercer, aka Lutessa Luthor (Cassidy Freeman), was created to fill the spot left by Michael Rosenbaum's Lex Luthor in Season 8. Tess is an amalgam of the most infamous of Lex Luthor's female counterparts from various sources; Miss Teschmacher (Valerie Perrine) in "Superman: The Movie", Mercy Graves (Lisa Edelstein) in "Superman: The Animated Series", and Contessa Del Portenza from the comic book series.
Due to the Batman embargo that Warner Bros. laid down due to the new Batman movie franchise, Oliver Queen/the Green Arrow essentially replaced Bruce Wayne/Batman. Batman himself would be featured in the comic book continuation of the series, "Smallville: Season Eleven".
Margot Kidder's character, Bridgette Crosby, was meant to become the primary villain of Season 4. After Christopher Reeve's untimely death in 2004, the show's producers decided to incorporate the death of the legendary actor into the plot as his character Virgil Swann was killed off screen. Kidder was not happy with this decision, feeling the producers were capitalizing on the actor's passing. Thus, she backed out of her commitments. As a result, the character of Genevieve Teague, as played by Jane Seymour, was created to fill in as the central big bad for the remainder of the season. Ironically, Christopher Reeve played a romantic love interest opposite both Margot Kidder and Jane Seymour; Kidder in Superman (1978) and Seymour in Somewhere in Time (1980).
The Smallville High Student Newspaper that Clark and Chloe write for is named "The Torch," after the student newspaper at Glenville High School in Cleveland, Ohio. Superman creators Jerry Siegel and Joe Shuster worked together on the Glenville Torch while they were students.
The rooms in the show will usually have something that is Red, Blue and Yellow this can include wall color, furniture etc. Also there are times where the coloring in the room (such as the Smallville Medical Center) that the colors of Green and Purple are used (Lex Luthor's old colors from the Superman comics).
The name of one of the Kryptonian baddies from season 5 is named Nam-Ek, the same name of the race of aliens come to earth (the race of aliens that Piccolo hails from) in the anime Dragonball Z. Nam-Ek is also the name of one of the Phantom Zone criminals in the DC Comics Superman titles, first appearing in Superman #282 (December 1974).
Belle Reve is the name of the estate that Blanche and Stella DuBois come from in Tennessee Williams's "A Streetcar Named Desire". Throughout the play, Blanche gradually becomes insane. In Smallville (2001), Belle Reve is the name of a mental hospital. In DC Comics, Belle Reve is the name of a federal prison for super-villains; it is located in Louisiana.
In Season 2, Lex Luthor shows Ryan the first issue of the Warrior Angel in a showcase. In the comic cover, Warrior Angel holds a car above his head. In Superman's first issue, Superman also holds a car above his head in the exact same position.
The first live-action appearances of several DC comics characters such as Pete Ross, the Suicide Squad (and its characters Amanda Waller, Deadshot, Rick Flag, Icicle, Plastique and Warp), Cyborg, Stargirl, Wildcat, Doctor Fate and Aquaman (if excluding the Aquaman (2006) pilot).
It's visually heavily inspired by the Superman (1978) film series though having it's own mythology and storyline. Some aspects such as Krypton and the Fortress' designs and Krypton's explosion are directly taken from the films.
On one of the Season One DVD commentaries, John Schneider said, while walking down the street, one day, two boys came up to him and said: "You are Jonathan Kent!" He said that he was relieved, because for the first time since The Dukes of Hazzard began, somebody recognized him as somebody besides Bo Duke.
Michael Rosenbaum (Lex Luthor), John Glover (Lionel Luther), Allison Mack (Chole Sullivan), and guest star Michael Ironside (General Sam Lane) provide their voices in the DCAU series and animated movies.
The trivia items below may give away important plot points.
Since the start of the "Superman" comic book, there has been an abundance of characters with the initials "L.L.," including Lex Luthor, Lana Lang, Lois Lane, Lori Lemaris, Lucy Lane, Linda Lee, etc. "Smallville" continued that naming tradition with several of the characters created for the show, including Lex's parents, Lionel and Lillian Luthor, his brother, Lucas Luthor, and Lana's parents, Laura and Lewis Lang. It is also revealed in a later episode that Tess Mercer's original name was Lutessa Luthor.
With both Chloe and Lana, Clark is tricked into revealing his abilities in front of them. In Season 4, Alicia sets things up so that Clark will show off his abilities for Chloe, and in Season 6, Lana sets things up so that Clark uses his abilities while she secretly watches.
After the 15th episode of Season 10 aired, Smallville took the crown (and the Guinness World Record) for being the longest consecutively running Sci-Fi television serial of all time (10 years without a break). Stargate SG-1 (1997) holds that title with 213 episodes, which Smallville will supersede by 5 episodes by the end of Season 10 (it's final season). Doctor Who however holds the record for the longest running Sci-Fi show in the world, running from 1963 to 1989 and 2005 to 2013, totalling 50 years. Doctor Who is continuing to this day with its 9th series starting in September 2015. Showrunner Steven Moffat stated Doctor Who will run for another 5 years with a feature film set to be released in 8 years.
The first and last close shots of Michael Rosenbaum (as Lex Luthor) are identical. In the series premiere he leaves his car out of the Luthorcorp plant, and appears as President Lex Luthor in the series finale in a very same manner.
In the 'Sacred' episode of Season three, when Virgil Swan's death is announced, the reporter says, "... and now to our on scene reporter, Tom Flores." 'Tom Flores' is the associate producer of "Smallville".
Clark's general fear that he might not be able to keep from hurting Lana during physical intimacy and especially his tense season five conversation with Chloe about this are references to a classic 1969 essay by science fiction author Larry Niven called "Man of Steel, Woman of Kleenex." In that article, Niven postulates that Superman/Clark Kent would be unable to have a sexual relationship with a non-superpowered woman, since his involuntary lack of physical control could result in catastrophic injury to his partner.
A "Chlois" theory was developed by fans who believed the character of Chloe Sullivan was this series' version of Lois Lane. The theory lived on even after Lois herself was introduced, with the "possibilities" that Lois would die or the two would switch identities.