Despite hardly any research to go off of there are several historical facts present: The Batiatus ludus and its massacre, the major battles between Spartacus and Rome, and the main gladiators: Spartacus, Crixus, Gannicus, and Oenomaus as well as their deaths (except for Spartacus as his death was not recorded). Even Spartacus' tactics such as sending fake envoys and sneaking into camps at night is historically accurate.
The Late Andy Whitfield died at the age of 39; roughly the same age as his on screen character Spartacus at the time of his death. Some historians have dated Spartacus to have been between the ages of 37 and 40 at the time of his death in 71. B.C. The most commonly agreed age, was 38 years old.
The wooden training swords used by the gladiators appeared to be very light and easy to handle. Historically speaking, wooden training swords for Gladiators were actually made to be heavier than steel swords in order for their handling of a Gladius to be more efficient.
Within the first 2 seasons, viewers see Glaber's ambitions at making a name for himself within the Senate and the Roman Government in order to leave his mark on history. In reality, the only thing that history knows of Praetor Claudius Glaber, is that he was the first of many Generals to fail at stopping Spartacus.
In September 2010, Andy Whitfield (Spartacus) announced that he would not be able to appear in the second season because he had been diagnosed with Non-Hodgkin lymphoma and was pursuing aggressive medical treatment. In January 2011, the Starz network announced that Australian actor Liam McIntyre had been chosen to replace Whitfield as Spartacus. In September 2011, Whitfield died at the age of 39.
Oenomaeus, Gannicus, Crixus and Spartacus were each Champions at one point, but came to it differently. Crixus and Gannicus were both Champions of the House of Batiatus before becoming Champion of Capua. While Oenomaeus was solely Champion of the house; never becoming Champion of Capua and Spartacus was never Champion of the house.
A feature-length movie was planned, it was to take place between season 2 and 3, but the writers realized that too much would need to be cut in order to avoid an NC-17 rating in the US, so the idea was scrapped
Despite this being an American series, the only actors who are American are Katrina Law (Mira), Erin Cummings (Sura), and Ellen Hollman (Saxa). Nick Tarabay (Ashur) is an American citizen, however he was born in Lebanon.
The final credit sequence ends with a shot of Liam McIntyre, which then briefly stays on screen as Andy Whitfield comes on before disappearing. It is the first - and only - time two men who portrayed the legendary gladiator were in the same scene as the character.
The brutal decimation scene is historically accurate. The only thing that the writers took liberties with is the character of Tiberius; everything else - the rogue sentry attacking Spartacus (and losing), the survivors running away - are all true. Crassus brought back decimation to ensure that his men would never run away again.
Recent research on Gladiator tombs in present day Turkey indicate that the fighters may have been on vegetarian diets, that likely consisted of grains and beans that would increase their body sizes around their abdomens. This essentially added a layer of body fat and muscle to protect their internal organs when stabbed or sliced. Some murals depict gladiators with literal barrel-like chests.
According to 'Steven DeKnight', the network wanted more of a 300 (2006) style of direction. This is why the pilot episode feels so out of place and the earlier episodes are uneven. DeKnight had to fight for control over the show.
The first season takes place over the course of 1-2 years; Vengeance takes places a few weeks after the ludus massacre; the third season has the biggest time jump of at least 2 years. This was done so that the show would go straight to Crassus' involvement rather than the other generals and battles that had occurred while Spartacus amassed his army.
Prominent Gladiators in the series, had pseudonyms; names describing either their victories or their fighting prowess. Arkadios was "The Scourge of Athens." Barca was "The Beast Of Carthage." Crixus was "The Undefeated Gaul." Theokoles was "The Shadow of Death." Spartacus, had a few names. "The Bringer of Rain" (the most frequently used) "Slayer of Theokoles", "Slayer of the Shadow" or "Slayer of Death."
'Dan Feuerriegel' is the only actor from the original cast to appear in the final battle; Spartacus and Naevia both appear but Liam McIntyre and 'Cynthia Addai' - Robinson both took over their respective roles from Andy Whitfield and 'Lesley Ann-Brandt'.
For the orgy scenes, the producers hired a New Zealand company that works on sexual gatherings professionally and instructed them to do whatever they wanted on camera. Then they would edit what was too much for Starz.
Throughout the first Season, Spartacus is ridiculed by his fellow Gladiators because of his Thracian heritage. Everything from his fighting prowess, to the alleged "filth" of his homeland fell under scrutiny; particularly from the Gauls. Some Historians however, believe that Thrace was among the more difficult provinces for the Roman Republic to conquer due to the fabled skill and "savagery" of the Thracian warriors.
Water is a very important theme throughout the series: the House of Batiatus was in debt (or was dry) during Crixus' run as champion but became wealthy when Spartacus took up the mantle after his victory ended the drought; and several characters die during a rainstorm or when one is approaching.
Every villain is tied to the house of Batiatus in some way: Lucretia, Quintus, Ashur, Ilithyia and Glaber all lived in the house at some point for an extended period of time; Marcus Crassus is connected through his cousin, Licinia, who was murdered by Ilithyia. Ironically, the show never touches on Marcus' connection.
The character Barca was initially written as Oenomaeus the Gaul. However Antonio Te Maioha who had been cast for the role was only available for 6 episodes of filming. So, his characteristics (mainly his bond with Crixus) were re-written to the new character Barca. The Writers then changed the identity of Doctore to be revealed as Oenomaeus.
Lucy Lawless was originally not to return for Series 2, which would had seen Lucretia die from her stab wound by Crixus. But, Lucy Lawless had proved popular on the set and with the cast and the producers were impressed with Lawless's performance as the evil and manipulative Roman woman. And in Series 2, it was revealed Lucretia survived her stab wounded and became delusional following the massacre and the baby died.
The character Barca ("The Beast of Carthage") shares the name of Hannibal Barca, the Carthaginian general who crossed the Alps on Elephant back to attack Rome. Hannibal also had a younger brother named Mago, in the episode "Legends", it is revealed that Barca earned his title by slaying the leader of his people, named "Mago", who was rumored to have also been Barca's father.
In addition to the 5 actors that went on to play comic book characters in TV show Arrow (Manu Bennett, Cynthia Addai-Robinson, Katrina Law and Nick Tarabay), and movie The Suicide Squad (Jai Courtney) Liam McIntyre who plays the title role of Spartacus plays villain Mark Mardon (Weather Wizard) in The CW's Arrow spin-off The Flash.
Crixus is the only character to be friends (at some point) with all the prominent gladiators from all three seasons and its prequel. Spartacus' only friend was Varro in the first season; Agron never met Barca; and Gannicus never met Varro.
Each season of the series, features a character named "Tiberius." In Season 1 "Blood & Sand", Tiberius is the name of one of the Gargan twins that Crixus defeated. In Season 2 "Vengeance", Tiberius is Nasir's slave name given to him by his master. (Which he never liked and stopped using once he accepted his freedom) In Season 3 "War of the Damned", Tiberius is the name of Marcus Crassus' son.
There is some irony surrounding the casting of 3 of the main characters. Spartacus was from Thrace, particularly modern day Bulgaira. Crixus was from Gaul, which is modern day France. Varro was Roman, which meant he was Italtian. The actor who portrays Gnaeus is himself Bulgarian./Historically, Crixus was a Frenchman with Curly hair. Jai Courtney being the fair-skinned, curly haired actor would have been the "accurate" choice for Crixus, but instead portrayed Varro. Manu Bennet is of the Maori tribe in New Zealand (who can virtually pass for any ethnicity) and would have been the ideal "visual choice" to play the Italian Varro.
Nick Tarabay, Cynthia Addai-Robinson, Katrina Law, Manu Bennett and Jai Courtney all went on to play roles based on comic book characters. Courtney (as [Captain] Boomerang) in The Suicide Squad (2016) and the others in The CW's Arrow (2012) (Captain Boomerang, Amanda Waller, Nyssa Al-Ghul and Slade [Deathstroke] Wilson respectively).
To distinguish which version of Spartacus they are talking about, fans have dubbed Andy Whitfield's portrayal as "Andy Spartacus" and Liam McIntyre's performance as "Liam Spartacus". Other variations include: "AS/LS", "Andy's Sparty/Liam's Sparty".
When Nasir is first introduced, he shares with Agron his Syrian heritage and that he had an older brother. The remote possibility of his older brother being either Dagon or Ashur, is not touched upon after that conversation.
Agron, Ashur, Nasir, Donar, Lugo, Varro, Hamilcar, Barca, Duro, Heracleo, Rhaskos, Pietros, Nemetes and Kerza are the only male characters of note whose names do not end with the letters (or pronunciation of...) "us." Equally, Kore and Sibyl are the only female characters of note whose names do not end with the letter "a" and the pronunciation of "uh."
The trivia items below may give away important plot points.
Andy Whitfield (Spartacus) stated numerous times that the reason his on screen friendship with Jai Courtney (Varro) felt genuine is because it was. The two remained best friends until Whitfield's death.
In the scene where Spartacus dies, the script called for Laeta to kiss Spartacus goodbye. It was changed at the last minute so that Agron would be the one who kisses Spartacus' forehead at the behest of Dan Feuerriegel. The actor felt it would be more emotional coming from someone Spartacus considered a brother.
Viva Bianca stated that both Ilithyia and Lucretia were meant to die in the ludus massacre; but DeKnight changed his mind when Andy Whitfield was diagnosed with cancer and Lesley Ann-Brandt chose not to renew her contract. He felt the changes would be too much for viewers to accept so he brought back as many familiar faces he could to help with the transition.
Not one character or actor appeared in every episode of the show (including the prequel mini series Spartacus: Gods Of The Arena). Crixus (Manu Bennett) is in the most episodes, being absent from only the final two. Even the titular character Spartacus is completely absent from the prequel series and the character of Naevia is portrayed by two different actors and the character is also absent from two episodes.
Crixus and Spartacus fight each other at least 8 times throughout the series. Seven of those fights occur within the first season and one occurs in the final season. Of these fights, 3 were fueled by anger, 3 were sparring sessions and 2 were scheduled matches.
Vettius is the only villain from the series (including the prequel "Gods of the Arena) who's ultimate fate remains unknown. He along with Crassus and Caesar are the only main villains who are not killed during the duration of the show.
Agron was originally supposed to die during the massacre instead of Duro; the writers changed their minds since Agron was always saving his brother, they felt it would be more emotional if Duro repaid the act.
Among the numerous Gladiators from the House of Batiatus who were taught that death in the arena at the hands of a Gladiator was a "glorious death" only 6 achieved such deaths (including characters from the show's prequel, but were all under less than ideal circumstances). The first Doctore, was killed by Oenomaeus (but not in the arena). Auctus was killed by Crixus in the arena (however, Crixus entered the Arena absent the mark of the Brotherhood and did not become a Gladiator until he slew Auctus). Dagon was killed by Ashur (but Ashur sabotaged Dagon first during elimination rounds in training and again during the battle royale). Gnaeus was killed by Spartacus in a fit of rage (but not in the arena). Varro was killed by Spartacus at Numerius' birthday celebration (during a match that was meant only to be exhibition and only through the machinations of Ilithyia). And finally, Rhaskos was killed in the arena by other Gladiators (but it was during his execution, not a fair match).
Foreshadowings of several character deaths occur within the first few episodes: Spartacus is shown being an expert with the spear - that is what kills him; Varro and Spartacus have a discussion about who Spartacus wants dead in the ludus but Varro is not one of them - Spartacus kills Varro; Ilithyia wonders what keeps the gladiators from breaking free and killing everyone - gladiators slaughter the guests in a massacre.
The majority of the rebels find their demise in a similar fashion. They are either attacked when they are off guard or attacked from behind. Brictius is killed from behind. Spartacus and Crixus both sustain injuries from behind that lead to their death. Lugo gets stabbed from behind which quickens his death. Chadara gets shot with an arrow from behind unintentionally. Naevia and Diona die in a similar fashion, killed from behind while on their knees. While Saxa gets killed from the front while she is distracted.