At the MK, a train with characters comes into the entrance area (after you walk through the turnstiles, but before you enter the park). A song plays and then Mickey starts the countdown to the park opening.
I kid you not, people were acting like it was a rock concert - screaming and jumping up and down.
All in all, I thought it was pretty cool! It was even better, because we were able to ride all of the rides we wanted with minimal waits (most of the time, we were able to just walk right in).