There are probably three different interactions that will always be some of my favorites - Peter Pan, Rapunzel, and Flynn Rider.
Now, Peter Pan has always been one of my favorite characters - and even more so now since I am at the age where I have to 'grow up' and that is a terrifying thought. About two years ago I went to Magic Kingdom really early one morning to be in the first M&G session for Peter Pan. Once I got back to the queue line, I realized that I was the first one there, but the photopass cast member assured me that he was going to come out and I could wait there with her if I wanted. So, I did. And then... I see Peter come out of the door leading to the backstage, and I immediately had the biggest smile on my face (somewhere there is an amazing photo of this)! I was worried that since I was older, the character interaction wouldn't be that great, but I was proved wrong. Peter and I talked about anything and everything, but the best part was at the end when I had him sign my autograph book. Now, this book is one that I made myself, and the front cover has the quote "Keep Adventuring and Stay Not A Grown Up" while the back has a multitude of song lyrics and Disney related things. He spent a while just looking at the book and all the stuff I had written on it, which was absolutely amazing. Then, he gave me a hug and told me that I could "always find Neverland". I definitely was crying as I walked away.
This past October I got to meet Rapunzel and Flynn, and those were both really cool and special to me. I mentioned before that I have the fear of the character interactions not being as good since I am older, and for some reason I was really worried about that this fall - I guess cause I was close to 'officially' being an adult. I just was worried that the characters and their friends wouldn't be as engaging or really care about the M&G since I wasn't a little 4 year old. (I know now that this was a stupid fear!) Anyway, I was walking over by the International Gateway when I saw Flynn and proceeded to freak out (which included lots of pointing and saying "MOM! Look!"), and went over to the line and ended up being the last person for that M&G session. When I got up to Flynn, I immediately knew I had nothing to worry about. He was so engaging and I could tell he really cared about talking to me. Perhaps the best part of that one was that when I went to take a selfie with him, he wouldn't let me stop - so I now have about 25 photos of me and Flynn Rider on my phone!
Later that day I was able to meet Rapunzel over at Magic Kingdom. I knew I shouldn't worry about the M&G, but I was hesitant on how it would be since she is a Princess and meets with lots of little kids every day. Once again, I had nothing to worry about. We talked for a good 5-10 minutes over all the adventures I had that day and even about Peter Pan. That was by far one of my favorite M&G I have ever had.
Meeting characters at Disney World is awesome just for being what it is, but to me, there's more to it than that. They let me realize that it doesn't matter how old I am, I can always be a kid and find Neverland and go on adventures with Rapunzel. And isn't that part of the core foundation of Disney - that we will always be kids on the inside no matter how old we get?