AThe cast lists really don't always list everyone, but that isn't the real reason here.Instead, while both Figaro the cat and Cleo the goldfish are supporting --> characters <-- in this cartoon, being animals they had no dialog, so no human voiced them, so there were no --> cast members <-- associated with them. So there were no cast entries made in IMDB, or in the film it may be, for them or other background characters of their nature, like Monstro the whale.Still, the Figaro character was reused by Disney in other films in which a human voiced him, and has his own character page, at http://www.imdb.com/character/ch0044450/. Cleo was also reused, the two are the subjects of "Figaro and Cleo (1943)" http://www.imdb.com/title/tt0035873/ .
AProbably to sell them and make money. He probably chose young boys because they were easier to manipulate (give a bad boy enough rope, and he'll soon make an ass of himself) and less likely to successfully retaliate than adults or little girls.The boxes that the donkeys are being loaded into have signs like "Sold to the salt mines" and "Sold to the circus," so he is selling them to various places.