Disney Monologue
One big secret in Hollywood is that the casting agent doesn't want someone in an audition to walk in and then assume the role using their acting skills. Instead, they want someone to actually be the role, from the moment they walk in. What does this mean? Well, it means there the a pre-conceived notion of the character. The actor who walks in the door already fitting that pre-conceived notion (before anyone says a word) is likely to get the role.
What does that mean for you? That means you walk in the door looking and behaving like a Disney character. How do you do that? You research other Disney characters by watching Disney movies and shows. Leading characters are all usually stereotypes, a handsome good looking prince, a beautiful but isolated girl, the all American quarterback. Sidekicks exists almost solely for comedic purposes, so if you are auditioning for the sidekick, be funny. Villains tend to scheme more than commit violence. So choose a monologue that fits the role you are going for.