I loved this thread on the Disneyland page but realized the majority of my CM magic stories were WDW related, so I wanted to start one here!
Many years ago, I was at WDW on a high school trip with our marching band and chorus, and traveled through each park with a group of 6 other girls. Since I had been to WDW many, many times, I always went on each trip with some sort of thing I had never done - in this case, I wanted to meet Cinderella, since I never had. I asked one CM earlier in the day and she couldn't give me a real answer, so I was feeling pretty defeated. Just as it was starting to get dark, we happened to be passing by the backside of Cinderella's Castle, and I asked a lone CM (who I'm sure was there to handle ushering people out of Fantasyland for the fireworks) if he knew where I could find Cinderella. He left me there for a moment, disappeared somewhere, and then came back out and said he heard she was at the Toontown Hall of Fame, but I'd have to hurry. All 7 of us started running, and got in an empty line at the Hall of Fame to wait. I don't know if the CM I spoke to warned the CMs at the Hall of Fame, but they seemed ready for us, and told us that since we had such a large group, they were going to take us out of line and bring us through the VIP passage. We got to meet all of the characters there by ourselves, and they let me go first to meet Cinderella, who knew my name ahead of time. It is one of my favorite memories.