* ActingForTwo: "X-Ray," "Visage," "Crusade," "Onyx," "Phantom," "Bizarro," "Persona," "Luthor," "Collateral"[[note]]for six, actually[[/note]], "Masquerade," "Kent."
* CaliforniaDoubling: With B.C. standing in for Kansas, this allowed for a {{Blooper}} once in a while, such as in the opening establishing shot of Metropolis in “Rogue”, where the TD Bank and Scotiabank logos can be seen on several skyscrapers. [[note]] TD does have a U.S. presence in banks and other financial services, but Scotiabank does not, making its logo a dead giveaway for the shot being filmed in Canada.[[/note]]
** Also happens in the Season 9 episode "Conspiracy," near the end when Chloe is wondering who took her Kryptonite weapons. In the background you can see E&H Hitch Shop, a real-life Vancouver business, as well as a sign showing their 604 telephone number (Vancouver's area code). For added rule of funny, the sign also has the name of an adjacent business with West Coast in its name--rather unlikely for Metropolis.
* TheCastShowoff: Alessandro Juliani and Creator/CassidyFreeman both have musical backgrounds, which is probably why they got to be the ones that sang in "Fortune."
* CastTheRunnerUp:
** Allison Mack toyed with the idea of auditioning for ComicBook/LanaLang before going for Chloe Sullivan. Incidentally, Allison is a green-eyed Caucasian just like traditional Lana, while Creator/KristinKreuk is part-Chinese with dark eyes.
** Originally actor Justin Hartley was supposed to play the role of the character Arthur Curry AKA Aquaman. However, he ended up playing the role of the Green Arrow instead and the role of Aquaman went to Alan Ritchson. Hartley played Aquaman in the producers' unsold spin-off pilot, ''Mercy Reef''.
* CreatorBacklash:
** Alfred Gough and Miles Millar [[http://web.archive.org/web/20171212140745/http://www.sundance.tv/series/the-writers-room/blog/2014/04/interview-with-smallville-creators-alfred-gough-and-miles-millar acknowledged they took the wrong decisions with Lana Lang]]. Gough said Lana's romance was a three-season love story that lasted six seasons and Millar said her response, although justified, made her seem [[UnintentionallyUnsympathetic cold and unsympathetic]].
** Laura Vandervoort considers that Kara didn't have a good closure in the series and thinks that [[TheyWastedAPerfectlyGoodCharacter her character wasn't explored enough]]. While she is understanding with her limited role given that the series focused on Clark Kent and Lex Luthor, she absolutely detested her Supergirl costume due to considering it too sexualized and has stated [[https://youtu.be/K1v8n-GtsRY?t=858 she wanted the staff to burn the wardrobe when she was done with her role]].
* CreatorBreakdown: Michael Rosenbaum has talked on his ''Inside of You'' podcast about becoming extremely depressed during contract negotiations with the execs, where they had "made all these promises" they weren't keeping, and would stay in his trailer between takes, to the point that Tom Welling became worried about him.
* DawsonCasting:
** In Season 1, Clark and his friends are high school freshmen (14-15 years olds). Creator/TomWelling was 10 years older than Clark (although justified, as Kryptonians tend to age faster). Eric Johnson (Whitney Fordman) was 25, Allison Mack and Creator/KristinKreuk were both 19; and Sam Jones III was just 18.
** Although it was never specified how old Lex was (possibly in his early 20s), Creator/MichaelRosenbaum was just 29.
** Creator/EricaDurance, who was 27 at the time of casting, played a 19/20-year-old Lois Lane.
* DirectedByCastMember:
** John Schneider directed the Season 3 episode "Talisman."
** Creator/TomWelling directed the episodes "Fragile" (his debut as a behind-the-scenes creator, a role he's actually continued in his post-''Smallville'' career), "Hydro," "Apocalypse," "Injustice," "Absolute Justice, Part 2," and "Patriot."
** Creator/MichaelRosenbaum directed the Season 6 episode "[[Recap/SmallvilleS06E15Freak Freak]]."
** Allison Mack directed Season 8's "Power" and Season 9's "Warrior."
* DyeingForYourArt:
** Michael Rosenbaum shaved his head every season to play Lex. Lucas Grabeel had to do likewise when he played the young Lex.
** Charlotte Sullivan, normally blonde, dyed her hair red to play Maxima.
** John Glover offered to have his long hair shaved as Lionel as long as it was done on camera.
** Erica Durance had blonde highlights when she started playing Lois to differentiate her from Kristin Kreuk. During the last two seasons, she went back to her natural brunette that Lois Lane is known for.
* ExecutiveMeddling:
** The producers of ''Smallville'' wanted Bruce Wayne to appear. The then-current owner of the ''Batman'' film franchise refused. The irony is Creator/DCComics owns both characters and, in the comic books, both Superman and Batman cross over all of the time and are, in fact, [[HeterosexualLifePartners best friends]]. Batman finally appears in the ''Season 11'' comics' second story arc.
** Stephanie Brown was to appear as Batman's sidekick, ComicBook/{{Nightwing}}, but Barbara Gordon was used instead.
* FakeNationality: Lia Teng is from North Korea, but her actress Françoise Yip is Chinese-Canadian.
* FridayNightDeathSlot: The show was moved to this in its second-to-last season, but remained one of Creator/TheCW's top shows. Its second season in this slot was its last, but that was less due to time slot and more due to factors such as various contracts expiring and a general feeling that it was time to finally end it.
* IAmNotSpock:
** Allison Mack expressed this sentiment on her blog.
** Averting Creator/ChristopherReeve's intractable marriage to the iconic role was among the reasons Tom Welling had insisted on "no tights, no flights" in his contract. But if the role doesn't stick to you after ten seasons, it's not going to happen.
* OneHitWonder: To this day, this is considered the only claim to fame for both Creator/TomWelling (until ''Series/{{Lucifer|2016}}'') and Allison Mack (until her sex trafficking scandal).
* TheOtherDarrin:
** Morgan Edge, through [[TheNthDoctor having plastic surgery]].
** Edward Teague had two different actors between the flashbacks in "Veritas" and his first modern appearance in "Quest."
* PromotedFanboy: John Schneider revealed that [[https://www.youtube.com/watch?v=E7Rxs1HNj0I he was already a Superman fan when he learned about the show and auditioned for the role]].
* RealLifeWritesTheHairstyle: Lana's ImportantHaircut in Season 8 was because Kristin Kreuk had been wanting to cut it for the past three years, so it was written into the storyline.
* RealSongThemeTune: Remy Zero's "Save Me".
* RoleEndingMisdemeanor: While the show was well over before Allison Mack's controversy came out, it effectively killed attempts to work the character of Chloe into the greater Superman mythos.
* ScullyBox: Allison Mack sometimes needed one, even with heels.
* SequelInAnotherMedium: After the series ended, an eleventh season was published in comic book form, following on from the events of the TV series and covering Clark fully embracing his Superman persona.
* StarMakingRole: For most of the cast, particularly Creator/TomWelling, Creator/KristinKreuk, Creator/MichaelRosenbaum, Creator/EricaDurance, Creator/JustinHartley, Creator/CassidyFreeman, Creator/SerindaSwan, Creator/LauraVandervoort, and Creator/JohnGlover.
* StuntCasting: The show stunt-cast many people previously involved in the franchise, including Creator/ChristopherReeve, Creator/MargotKidder, and Creator/TerenceStamp (as the voice of Jor-El!) from ''Film/SupermanTheMovie'', Creator/DeanCain and Creator/TeriHatcher (as Lois's mother) from ''Series/LoisAndClark'', Creator/HelenSlater from ''Film/{{Supergirl|1984}}'' (as [[ComicBook/{{Supergirl}} Kara]]'s mother), and so on.
* UnderageCasting: Jonathan Kent is stated to have been born in 1954, but Creator/JohnSchneider is actually six years younger, and nearly a decade younger than his on-screen wife Creator/AnnetteOToole.
* WhatCouldHaveBeen:
** Creator/MiloVentimiglia, Creator/JensenAckles and Creator/BrandonRouth auditioned for the part of [[Franchise/{{Superman}} Clark Kent]] before Creator/TomWelling was cast. Ackles would eventually go on to play Jason Teague, whereas Routh would portray the character in ''Film/SupermanReturns''.
** [[Series/PoltergeistTheLegacy Martin Cummins]], Creator/AnsonMount and Creator/ZacharyLevi read for the role of Comicbook/LexLuthor before the casting of Creator/MichaelRosenbaum. Cummins and Mount would later go on to play Dr. Garner and Paul Hayden respectively, while Levi would portray [[Comicbook/{{Shazam}} Shazam]] in the Franchise/DCExtendedUniverse.
** The writers planned to bring [[Franchise/{{Batman}} Bruce Wayne]] into the show at one point as a guest role, but this was shot down because of the then-upcoming [[Film/BatmanBegins Batman film]]. His role and storyline were apparently converted into Adam Knight instead.
** A relatively small one for Season 7: The writers originally planned for Lionel's death to be the final scene of an episode, not the opening for what became "Descent"; the following episode would have followed the remainder of the produced episode's plot, presumably. The 2007 Writer's Strike, while not hitting this show ''too'' hard, did see it cut from 22 to 20 episodes, and this along with two whole episodes needing to be cut from the plan was the result...arguably for the better, at that.
** The original plot for the episode "Shimmer" had an invisible villain disrupting a school play before it was changed to an invisible villain stalking and attacking Lex Luthor and his loved ones. The original plot was turned into the ''Smallville'' novel ''See No Evil''.
** Creator/SamWitwer was offered the part of Major Zod (the BigBad of season 9) but he turned it down, believing it wouldn’t make narrative sense for him to resemble the serial killer Davis Bloome.
** The creators [[https://portugal.postsen.com/celebrities/424026/Creators-confirm-that-Chloe-almost-became-Lois-Lane-in-the-series-%E2%80%98Smallville%E2%80%99.html confirmed years later]] that they had indeed considered making Chloe their version of Lois Lane, potentially having her change identities or use the name as an alias since they were legally prevented from using Lois in the show. However they were allowed to use her in Season 4, leading her to becoming a main character for the rest of the series.
* YouLookFamiliar:
** Creator/ShawnAshmore played Eric Summers in Seasons 1 and 3, but his identical twin brother [[Creator/AaronAshmore Aaron]] plays Henry James "Jimmy" Olsen in later seasons. Aaron returns in the series finale to play [[ComicBook/JimmyOlsen James Bartholomew Olsen]].
** The token Asian of the crooks that break into the [=LuthorCorp=] tower early in the series shows up in Season 4 as a Chinese national constable on the take. They're played by Creator/ByronMann of ''Film/StreetFighter'' fame.
** Jim Shield, who played Sylvester Pemberton aka The Star-Spangled Kid, previously played Ryan James' abusive step-dad in Season 1's "Stray."
** Creator/PascaleHutton played Karren Gallagher, the ill-fated mother of the rapid-aging Evan in Season 4's "Ageless" and Raya, the Kryptonian ally of Clark in Season 6's "Zod".
** Creator/ChristopherHeyerdahl played Dr. Arthur Walsh in the web series SpinOff ''The Chloe Chronicles'', and then played Zor-El in the series itself.

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