Jesus walked on water, calmed storms, and healed people, but did you know he could ride two donkeys at the same time?
That's what Matthew tells us in his version of Jesus' life (Mt 21). In preparation for his final entry into Jerusalem, he records Jesus instructing his closest friends to go into a village and find a "donkey, and a colt with her and bring them to me."
They bring the two animals to Jesus, throw their jackets on both animals and then Jesus hops on both of them! Matthew tells us Jesus did this to fulfill what had been spoken through the prophet, "Tell the daughter of Zion (Jerusalem): Look your king is coming to you, humble and mounted on a donkey, and on a colt, the foal of a donkey" (Is 62.11, Zech 9.9).
The other gospels only have Jesus riding on the colt and make no mention of two animals, so why would Matthew tell the story this way? It is most likely because he saw Jesus as the literal fulfillment of the words from Zechariah.
He is so serious about rooting these events in the authoritative Hebrew scriptures, that he chooses to ignore the poetic force of the passage and instead interprets it literally.
Mentioning the smaller donkey after the first is a way of strongly emphasizing the humility and peacefulness of the one riding the animal: "Your king is so humble and peaceful, that he rides on a donkey...not just a donkey, but a baby donkey."
Jesus rode into Jerusalem being touted by his followers as the triumphant deliverer of Israel, and Matthew more than any of the other gospels presents the strongest contrast between Jesus and the rulers of the day.
Jesus rides into Jerusalem on two animals, struggling to keep his balance, on his way to inaugurate a revolution of peace. In this revolution people lay down their lives instead of taking them, and what could be a more brilliant picture of their peaceful founder than that.