Most of the people that are selected for shows and parades have some dance and/or acting experience. Keep in mind though, that even if you aren't in a show or parade, you'll still have to act. Even though most of the characters cannot talk, they still interact with kids, and need to figure out ways to "hold a conversation" in pantomime, and behave as the character would.
That might mean that Chip and Dale need to act goofy and play tricks on each other, or that Donald may need to "have a fit" if someone says Mickey is better than he is, etc, etc.