Mary is a character from Disney's 1978 animated Christmas short film, The Small One, being the actual Virgin Mary from the Bible. Although her name is never mentioned in the entirety of the film, it is pretty obvious that she is the one who rides Small One with her husband, Joseph to Bethlehem. Joseph's line in the short film: "I need a gentle donkey to carry my wife to Bethlehem." says it all. Her son is Jesus.
Mary only appeared for a short while in the film, because she was seen at the very end. She was first seen with her husband, Joseph riding on Small One (bought by Joseph from a boy earlier at night) while waving good-bye to the boy from a long distance and then, continuing their journey to the manger in Bethlehem where a bright star later shone; symbolizing the birth of their son, Jesus.
The "Hellfire" sequence of the film consists primarily of Frollo's prayer to the Blessed Virgin Mother Mary. Roman Catholics do pray to Mary to ask her to pray to God on their behalf, and because of her absolute purity she is the perfect saint to ask regarding his inappropriate attraction to Esmeralda. However, in so doing Frollo reveals himself to be filled with sinful pride, lust, envy, and vengefulness.
Earlier in the movie, the Archdeacon sang "you can never run nor hide what you've done from the eyes, the very eyes of Notre Dame". This was the Archdeacon's way of saying that, from Heaven, the Virgin Mary bore witness to Frollo's murder of Quasimodo's parents, and thus Frollo needed to do something to avoid being damned by her. This is what convinced Frollo to adopt Quasimodo as his son.