In his memoirs, "Dear Me" (1981), Sir Peter Ustinov recalled that MGM had sought him for the role of Emperor Nero but dithered for months, refusing to commit. During this time, he received numerous telegrams from the studio, one of which stated that they were concerned that he might be too young to play the notorious Roman Emperor. Ustinov replied that Emperor Nero died when he was thirty, and that if they waited much longer, he'd be too old. The studio cabled back: "Historical research has proved you correct. You have the part." Coincidentally (or not), Ustinov was 30 years old when this movie was released.
The movie's huge box-office success was credited with saving MGM from bankruptcy.
According to the film's press book, it used 32,000 costumes, a record at the time.
Marcus is shown taking his bath in a fairly accurate way. Romans did not have soap - a thing that, along with towels, would not be introduced to Europe until the arrival of Islam. Instead of soap, they would pour oil over the skin and then use a curved tool known as a strigil to scrape off the oil and dirt. If the strigil had a slight edge, it would also lightly scrape the skin, which removed old skin cells and prompted a stimulating flush of blood flow.
Despite the happy ending to the film, the reign of Nero's successor Galba was a short-lived disaster.
Sophia Loren: strewing flower petals in the path of Marcus Vinicius' chariot during the triumphal march. While not her first movie, it is her first American movie, albeit shot in Italy.