The series takes place over more than 20 years, but some of the characters don't age over that time.
In real life, Servilia died after Atia.
The cast says Domina and Dominus frequently. They're used in the vocative; the masculine form would be Domine.
Several historical changes were made to move the story along. Octavian was in Illyria undergoing military training when Caesar was killed. Livia was Octavian's third wife. When she married him, she had two sons, Drusus and Tiberius. Drusus was married to Antonia, daughter of Marc Antony and Octavia, and was the grandfather of Caligula and father of Claudius. Octavian had one natural child, Julia, by his first wife. Julia was married to Tiberius.
The series left out or changed details of actual history in many instances. Pompey was only 6 years older than Caesar. Octavian was called Octavius until after his posthumous adoption by Caesar. At the start of the series (52 BC), Octavius is living in his mother's household. However, Octavius was raised by his grandmother until her death in 51 BC. Atia was married to Lucius Marcus Philippus from 56 BC until her death in 43 BC. Brutus committed suicide after his and Cassius's defeat at Philippi. As a show of great respect, Mark Antony ordered Brutus' body to be wrapped in Antony's most expensive purple mantle. When Octavia married Mark Antony, she already had 2 (possibly 3) children; her first husband died in 40 BC. Although left out entirely from the story, Porcia, Brutus's wife, is rumored to have played a much larger role than Servilia in planning Caesar's assassination. Porcia committed suicide after Brutus died.
Slaves at auction wear loin cloths. Young women, and slaves being sold as laborers, were displayed naked.
In the series, Octavian's mother, Atia, is alive in 31 BC. She died in 43 BC.
In one scene, a character is suddenly awoken. He yells out "Oh, Jesus!".
This is taking place decades before Jesus's time.
In the series, candles are the primary source of lighting. Romans mostly used oil lamps.
In the close-up views of sandals, especially the legionaries' sandals, a modern rubber sole is visible. Shoes of the period had leather soles.
According to the DVD commentary, the creators included camels in scenes set in Egypt to make them look exotic compared to Rome. Camels were useless in ancient Alexandria. It was built on a marshy island in the Nile delta, and it's very hard for camels to walk over soft, humid soil.
Captive birds are shown frequently, including Macaws and Amazon parrots from America, and cockatoos from Australia. Those continents were unknown to the Romans; they wouldn't have traveled to obtain the birds.
In the series, Cato is much older than Cicero and Pompey. He was actually more than 10 years younger.