From volume four of "The Lives of the Twelve Caesars" by C. Suetonius Tranquillus as translated by Alexander Thomson and revised by T. Forester.
"... It was to the jokes of the soldiers in the camp that he owed the name of Caligula, he having been brought up among them in the dress of a common soldier. ..."
"...He delighted in witnessing the infliction of punishments, and frequented taverns and bawdy-houses in the night-time, disguised in a periwig and a long coat; and was passionately addicted to the theatrical arts of singing and dancing. All these levities Tiberius readily connived at, in hopes that they might perhaps correct the roughness of his temper, which the sagacious old man so well understood, that he often said, 'That Caius was destined to be the ruin of himself and all mankind; and that he was rearing a hydra [392] for the people of Rome, and a Phaeton for all the world.' ... "
“He would display the keenest enthusiasm about various projects, and then carry out certain of them
in the most indolent fashion. He would spend money most unsparingly, and at the same time show
a most sordid spirit in exacting it. He was alike irritated and pleased, both with those who flattered
him and with those who spoke their mind frankly. Many who were guilty of great crimes he neglected
to punish, and many who had not even incurred any suspicion of wrong-doing he slew. His associates he either flattered to excess or abused to excess. As a result, no one knew either what to say or how to act toward him … This was the kind of emperor into whose hands the Romans were then delivered. Hence the deeds of Tiberius, though they were felt to have been very harsh, were nevertheless as far superior to those of
Gaius as the deeds of Augustus were to those of his successor.“
“… the boy Gaius was called by them Caligula, because, having been reared largely in the camp, he wore military boots instead of the sandals usual in the city.”
“… at another time he was playing at dice and finding that he had no money, he called for the census lists of the Gauls and ordered the wealthiest of them to be put to death; then, returning to his fellow-gamesters, he said: ‘Here you are playing for a few denarii, while I have taken in a good hundred and fifty millions.’ So these men perished without any consideration. …”
“Caligula imagined that there now remained no man of sufficient consequence to raise a party against him, or to interrupt him in the tyrannical exercise of government …”
“… the emperor flattered himself that his wisdom, moderation, valor, justice, and other qualifications had rendered his character so distinguished, that it was incapable of greater perfection…”
"When he stood upon his royal palace and threw gold and silver pieces of money among the people, he might have been pushed down headlong, because the top of the palace that looks towards the Forum was very high."
"...'He (Caligula) built villas and country houses with utter disregard of expense . . He built moles out into the deep and stormy sea, tunnelled rocks of hardest flint, built up plains to the height of mountains and razed mountains to the level of the plain.' Of all these magnificent monuments by which not merely Rome but the Roman world was filled and on which was squandered the revenues of a realm there are left to us in Rome itself but a few fragmentary walls, and a broken but precious cistern, safely locked away for future ages in its tomb fashioned by the walls of the later imperial palace. ..."