Caligula was the third Roman emperor, in succession to Tiberius, the son of Germanicus and the great-grandson of Augustus.
Caligula became ruler of the Roman Empire in 37 CE and three years later he declared himself to be a deity. Soon after he ordered that every temple or place of worship in the Roman Empire make an statue of himself and worship it. The Jews in Jerusalem refused to worship a statue of him in God's Temple as the true Israelite could not worship an image.
Caligula was angered by the Jews refusal to worship his image and threatened to destroy their Temple. However Caligula was killed in 41 CE and the Jewish Temple would be spared.
Emperor Caligula's threat to defile the Temple with his image had greatly offended the Jewish people, they were worried in case the next emperor would again try to defile the Temple. Decades after the death of Caligula, the Romans in Jerusalem would expose themselves in the Temple and even burned a Torah scroll.
Caligula's action were one of the many reasons why the Jewish people tried to rebel against the Romans in 66 CE.