Donkeys are plain, humble creatures. There is nothing at all fancy or glorious about them. But they are good servants to humans. They do their job without vanity or ego.
Jesus came, the first time, as a humble servant. Throughout His entire life, from Bethlehem to Nazareth to Capernaum, He lived and dressed simply and modestly, despite Who and what He was, and the incredibly important and glorious mission that He was on. His entry into Jerusalem was of solemn humility (in fulfillment of the prophecy written in Zechariah 9:9):
"As they approached Jerusalem and came to Bethphage on the Mount Of Olives, Jesus sent two disciples, saying to them, "Go to the village ahead of you, and at once you will find a donkey tied there, with her colt by her. Untie them and bring them to Me. If anyone says anything to you, tell him that The Lord needs them, and he will send them right away." This took place to fulfill what was spoken through the prophet: "Say to the daughter of Zion, 'See, your king comes to you, gentle and riding on a donkey, on a colt, the foal of a donkey' The disciples went and did as Jesus had instructed them. They brought the donkey and the colt, placed their cloaks on them, and Jesus sat on them. A very large crowd spread their cloaks on the road, while others cut branches from the trees and spread them on the road. The crowds that went ahead of Him and those that followed shouted, "Hosanna to the Son of David! Blessed is He who comes in the Name of The Lord! Hosanna in the highest!" (Matthew 21:1-9 NIV)
What a wonderful honor it must have been for those people (and even for the donkey and her colt) to have taken part in what has become known as the "Triumphal Entry".
Fact Finder: Does God look with favor upon the humble?
(a) yes (b) no
1 Peter 5:5