Who they were
Caligula — formally Gaius — was the third Roman emperor, a son of the popular general Germanicus and a great-grandson of Augustus. His nickname, meaning little boots, came from the miniature soldier’s gear he wore as a child in his father’s camps.
What they did
Acclaimed with enthusiasm in 37 after the dour Tiberius, he fell gravely ill within months, and the ancient sources describe the reign that followed as increasingly cruel, extravagant, and obsessed with his own divinity. Famous stories — above all that he planned to make his horse Incitatus a consul — are reported by hostile writers such as Suetonius and may be exaggeration or satire. His spending strained the treasury, and in January 41 officers of the Praetorian Guard led by Cassius Chaerea assassinated him; the Guard then proclaimed his uncle Claudius emperor.
Legacy
His name became a lasting synonym for mad tyranny, revisited endlessly in drama and film. Historians caution that the surviving accounts are uniformly hostile, and separating the man from the anecdotes remains difficult.