Did Donald Duck ever have to audition? What about Mickey? Mickey probably had an inside connection with old Walt, bar-hopping in the Florida Keys or some such thing. How does one find out about casting calls for Disney? Pinocchio was discovered whittling souvenir key chains in a wood lot outside Bacontown, Maine. Little Mermaid was toughing it out on the swimsuit modeling circuit. These guys really paid their dues.
Today, unless you are bar-hopping with Steven Jobs, majority owner of Disney Corporation, you still have to audition for Disney productions, but the process for accessing the information you need about when and where those casting calls are being held is a little more stream-lined. The old-school studio system made it a little more difficult to break in, but nowadays info on Disney casting call opportunities is slightly easier to come by.
Even the folks playing the characters at the theme park itself had to audition, and although this is no guarantee that they will eventually work in a Disney production, being there does create the opportunity to find out about that next Disney casting call coming up for 101 Dalmatians four!