not rare now since the movie........but........in 06 they were rare.....tweedledee and tweedledum....they were down in the international gateway hollow a couple times that year.
I think the most "obscure" characters I've seen were Clarabelle Cow and Horace Horsecollar in Town Square. I don't think many people knew who they were. I don't recall how many years ago this was.
We found two of the female mice from Cinderella in Fantasyland when we visited in April 2000. Unfortunately, I don't have a picture on my computer. Those are probably the most obscure we have encountered. We also ran into the Beast at MGM...oops, I mean Hollywood Studios ... during the same trip. He's one we don't really see hanging around anymore.
I have a picture of us with Scrooge in November of 2007. It was taken right before you go into toontown (The stretch before Pete's garage). You are right he was in a Christmas getup.
For me, it was Jiminy Cricket on the Disney Magic last summer. I remember thinking at the time that I don't recall ever seeing him at either WDW or DLR.