 FACT: Caligula was emperor of Rome from 37 to 41 CE. The apostle  Peter is known to have been incarcerated by Herod Agrippa, who  reigned from 40 to 44 CE. When he came to Rome is unknown but this  must have been later, only after there were followers of the new  religion there (after 50 CE). So, Caligula and Peter were never in  Rome at the same time.