I saw Mickey in his one year only Halloween 'bat' outfit at Disneyland. I looked around several times that year during Mickey HalloweenTime, and only saw that Mickey once.
Hmmm...not sure about the rarest, but here are a list of rare ones I have spotted:
Big Al the Country Bear,
Suzy and Perla (Cinderella Mice),
Sheriff of Nottingham,
And Captain Jack Sparrow
I saw all of these in Disneyland Paris this August.
rarest character I've met would either be the Beast or Prince Charming...both at MVMCP.
I can now add Meg (from Hercules) to my list. I met her at Epcot a few weeks ago.
The Sheriff of Nottingham, when I was a kid. He grabbed my brother and lifted him off his feet. It startled him and made us all laugh. We had no idea who he was and debated it all day.
Rarest one I've met recently was the Hag from Snow White. I also have a great photo with Snow White and all Seven Dwarves.
Back growing up, it was probably Orville from the Rescuers.
Tarzan... that was some meeting. They need to bring him around more often.
i met tom morrow once
We won't be back for a couple of years but I'm gonna have to research Meg for her. See if I can find her. Any chance you have a pic of her?