Think of it as the ancient equivalent of miniature Nikes and tuxedo-imprinted onesies: Even in Roman times, parents liked to proudly dress their progeny in tiny versions of grownup gear. And so, when the respected general Germanicus brought his son Gaius on campaign, the tyke sported soldier’s footwear, or caligae, scaled down to his size. (Some scholars think his wife Agrippina, granddaughter of Emperor Augustus, chose the getup to emphasize her family’s imperial pedigree.) Either affectionately or mockingly, Germanicus’ troops called the boy “Caligula,” meaning “Little Boots” or “Booties.” The nickname stuck, but Gaius reportedly hated it.

Growing up, Agrippina the Elder had a close relationship with her grandfather, Emperor Augustus, who personally oversaw her education. After marrying Germanicus, she defied tradition by accompanying him on his military campaigns in Germania, reportedly acting as an adviser and diplomat. When Germanicus died under suspicious circumstances, Agrippina boldly accused one of his rivals of poisoning him.

A prominent figure in political circles, Agrippina the Elder also spoke out against Augustus’ successor Tiberius, whom she hated. All this rabble-rousing didn’t sit well with the emperor, who had Agrippina flogged—supposedly until she lost an eye. She then starved herself to death while in prison, four years before her son Caligula came into power.

It was Suetonius who first published claims that Caligula committed incest with his three sisters. (The Roman historian added that these trysts even occurred during banquets, as guests and Caligula’s wife gathered around.) But Suetonius wrote “The Lives of the Caesars” in 121 A.D., 80 years after Caligula was assassinated at age 28 by members of the Praetorian Guard. Earlier chroniclers who actually lived under Caligula, namely Seneca and Philo, make no mention of this type of behavior despite their harsh criticism of the emperor. And Tacitus, during a lengthy diatribe in which he accuses Caligula’s sister Agrippina—wife of the Emperor Claudius—of incest with her son, never implicates her brother.

According to Suetonius, Caligula in his infinite profligacy once constructed a temporary floating bridge across the Bay of Baiae just so he could ride triumphantly from one end to the other. No traces of the stunt have ever materialized, so most historians dismiss it as myth. However, evidence of the emperor’s extravagant lifestyle has surfaced at Lake Nemi, where workers salvaged two massive pleasure barges—complete with marble décor, mosaic floors and statues—in the late 1920s and early 1930s. One of the wrecks included a lead pipe bearing the inscription “Property of Gaius Caesar Augustus Germanicus.” It is uncertain whether it was Allied or German troops who cause the fire that largely destroyed the ships in 1944.

Caligula is often remembered as a selfish and capricious ruler whose ineptitude weakened the Roman empire during his four-year reign. But if his leadership skills were so abysmal, some scholars have argued, how did he wind up annexing new provinces, expanding westward and formulating a feasible plan to take over Britain? Although Caligula got no further than the English Channel and was murdered soon after, his preparations for the invasion would allow Claudius to begin Rome’s successful conquest of Britain in 43 A.D.

These days, many historians reject the notion that Caligula terrorized Rome with his unbridled madness, talking to the moon, ordering arbitrary executions and trying to make his horse a consul. For one thing, his fellow lawmakers would likely have whisked him out of power for such conduct. But assuming the much-maligned emperor was the loon his chroniclers describe, some scholars have suggested that an illness made him come unhinged—possibly temporal lobe epilepsy, hyperthyroidism or Wilson’s disease, an inherited disorder that can cause mental instability.

In 1979 the film “Caligula,” directed by Tinto Brass and starring Malcolm McDowell, shocked the world with its explicit portrayal of the emperor’s cruel and salacious escapades. It was the first major motion picture that juxtaposed segments featuring respected, mainstream actors with scenes that were essentially pornographic. To this day, the highly controversial movie remains banned in some countries.