Ohmygoodness, it is so hard to pick! We have been lucky to have tried many of the character meals. We all love the Tusker House Breakfast but my favorite is 1900 Park Fare, because of some special Pixie Dust. Here's the story:
[Sidebar, preface: we took each of my 3 DDs by themselves for their first visit, the summer before 1st grade. This way we could focus on them and follow their lead, without making the oldest wait until the youngest was old enough, and avoiding arguments among the siblings. Plus this way DH and I got to go three times instead of just one first visit for all, LOL!]
The year we took my middle DD by herself (she was five) we had a reservation for the very first dinner time at Park Fare. I can't remember why we wanted that time, but that's how it worked out. The doors to the dining room weren't even open yet, so we had checked in and were waiting in that little "lobby" where they meet the Fairy Godmother (do they still do this?) and get photos taken. The manager was greeting the guests as we waited for the restaurant to open, and she chose my DD to do a little ceremony thing to officially open the dining room for the evening ("introducing Princess Rebecca of the Kingdom of New York, here on a royal mission to visit Cinderella...."). They open the French doors and there are two loooooong lines of the waiters and waitresses, down which path she was led to our table, hand in hand with Cinderella and Prince Charming! It was amazing. She was crying because she was so nervous and surprised. What a special moment for her, and she got SO much attention from everyone during the meal. It was fantastic.
After the trip we of course told my other girls about it, and my youngest decided she wanted to do the same thing when we took her for her trip. So over the next two years she would sometimes mention this and DH and I would tell her that the chances of this being repeated were unbelievably remote, things at the restaurant could have changed, they might not do this every day, etc. You know where I'm going with this, right?!
Fast forward two years and we are on the trip with my youngest DD and had made an ADR at 1900 PF for the earliest dinner time, and would you believe it but she gets picked for the same thing!? I was amazed. Now SHE was fully prepared for this and there were no tears -- she just waltzed right on in there with Cindy and Charming like she had been anticipating this for years (as she had!). I am still in awe that that happened twice. I guess maybe not that big a deal, but for our family it was just amazing. Even now, my eldest (now 13) will sometimes wistfully mention that she didn't get to do this on her trip (we ate there, but not right when it was opening - who knew!?)!

So this is a tip for any of you out there with little girls who might like to see if they could get a chance for this special honor. We loved it!
PS - I think I am going to add Ohana Breakfast to our list for this year, after reading everyone's posts! Sounds so great!