Twice jailed for drug use, Jay Robinson once had the dubious honor of being recognized by his fellow inmates when this film was played for the convicts.
The set of the Christian neighborhood in Rome has previously been used in The Robe (1953) (of which this film is the sequel) as the village of Cana. We can easily recognize the well with old broken columns.
According to Jay Robinson (Caligula), the break in principal photography between The Robe (1953) and this film was only three weeks. This would account for "The Robe"'s opening shot of the gladiatorial arena, a scene lifted from its sequel. The scene features Victor Mature and Robinson, in addition to Ernest Borgnine, William Marshall, Richard Egan and Susan Hayward; these last four were not in "The Robe".
A close-up view of one tiger growling shows that its top canines were removed.
Every Roman soldier in the film carries his sword on his right hip. Thus forcing viewers to conclude that every soldier in Rome is left-handed. On the contrary, the sword was always on the right hip, regardless of the soldiers' handedness. Roman soldiers carried the shield in their left hands.