I think I recall "special" characters being rumored one year for the retreat, and there was a rumor Dr. Strange was there. However I think it was just a rumor. I am guessing if there are characters they are just more of the finish line group of characters.
Years ago they would have unique characters at the finish line, but now it's pretty much the MVP'S.
I completely understand why they want the MVP's at the finish before anyone says anything lol.
On another note...and something I occasional need to vent about,
I just with they would get back to the years where they offered so many unique characters, I really think that is one of many small reasons the numbers are down. I know a lot of folks who used to run for the characters have stopped because of it. Paris has so many unique characters to chose from. Heck getting two or three of them a year would set that segment of the fandom on fire. It would probably pay off way more than the price of flying those characters over here, and "training" them in the States.
I know they have several characters ready here as well, I mean Dumbo, Rattigan, King Leonidus, Kronk, Kuzco, etc... have all been out for special events recently but none of them have ever appeared at the races.