When Suetonius recorded the life of the Roman Emperor "Caligula" (Gaius Julius Caesar Augustus Germanicus), he provided one of the more stunning portraits of reckless abusiveness in the history of human leadership. The Roman throne had hosted ambitious manipulators and ruthless generals, but none of them proved to be more dangerous than a self-absorbed, egomaniacal, pampered-from-birth, pompous, dynastic cynic—Caligula. His reign only lasted from 37 to 41, when his own guards assassinated him.
Frivolity and disrespect were the weapons Caligula wielded to try to destroy the empire. Caligula despised the senate for daring not to yield to his wishes, and he reserved the most ridiculous of his acts of disrespect for the senate. He auctioned off the wives of Roman senators, daring them to object. Suetonius even reported that Caligula considered appointing as Consul his favorite horse, Incitatus.
Consul was not the most important office in the empire, but it was an important office. It wasn't the equivalent of a presidency—more like a vice-presidency.
Don't misunderstand Caligula's motives. He loved his horse, but Caligula did not have any high estimation of his horse's capacity for governance. Caligula was not endorsing anything his horse had done or planned to do in public service. Caligula's actions revealed nothing about his agreement or disagreement with his horse on any sort of political platform.
Nevertheless, Caligula's action is historically significant. Although it reveals very little about Caligula's opinion of his horse, it reveals a great deal about Caligula's opinion of all of the Roman government except for himself. He did not take the government seriously. He disrespected it. As far as he was concerned, the senate deserved to have to deal with his horse Incitatus.