How Titus Pullo Brought Down the Republic - S1-E2
Corrected entry: There was no Roman named Marc Anthony, the man who was a friend of Caesars and later husband of Cleopatra was named Marcus Antonius. If they called him Marc Anthony at all times in the series that wouldn't be a mistake, since it would be "modernized" language, but in this episode they at one point refer to him as Marcus Antonius. If they acknowledge that this is his name it is an error for them to call him Marc Anthony in other scenes because it makes no sense.
Correction: The only time they call him Marcus Antonius, is when he is installed as a tribune of the plebs. That is an official ceremony, where he is likely to be called by his full name. Mark Anthony is the name everyone calls him by in daily business. I have a friend called Marcus, whom I always just call Marc.