The topic is inspired by nephilims. The apocryphal Book of Enoch vividly illustrates the complex relationship between celestials, extraterrestrials and humanity. In the Book of Enoch, a group of 200 extraterrestrial entities called the ‘Nephilim’, or ‘fallen angels’, come to Earth allegedly due to their attraction to human females. The Nephilim subsequently begin to interact with humanity by interbreeding: [Ch. 6:1] And it came to pass when the children of men had multiplied that in those days were born unto  them beautiful and comely daughters.
And the angels, the children of the heaven, saw and lusted after them, and said to one another: 'Come, let us choose us wives from among the children of men  and beget us children.' And Semjaza, who was their leader, said unto them: 'I fear ye will not  indeed agree to do this deed, and I alone shall have to pay the penalty of a great sin.'