We even play/sing a Christmas song about it.
There was no donkey. It is the invention of a much later story teller or illustrator.
Joseph went from the town of Nazareth in Galilee to the town of Bethlehem in Judea, the birthplace of King David. Joseph went there because he was a descendant of David. He went to register with Mary, who was promised in marriage to him. She was pregnant.
That is all that Luke tells us - Matthew does not mention the journey at all, as we shall see. It is inconceivable that a humble trader from Nazareth, together with his pregnant and unmarried wife-to-be, could have ever afforded to hire a donkey.
They walked. 100 miles. Probably at night because the days would be too hot. (no snow, remember?)
It gets worse! If there had been a donkey, Joseph would most likely have ridden it and Mary would have walked - that was the custom of the day.
Oh yes. Mary would not have worn a blue frock - such luxury was reserved for the wives of wealthy lawyers, politicians and businessmen.
The Birth of the Son of God becomes more and more unrealistic.
Which is a great pity.