It's actually a show/M&G that starts every hour, and the line of people waiting forms at Fairytale Garden and goes straight up the path towards the castle. The CMs will try to let those waiting know about where the cutoff for the next show is. You might want to check by every now and then and see how many people are waiting on the next show about 15 minutes before it starts late in the day, you might get a short wait.