I think the Muppets haven't been out for quite a while.
The Power Rangers are out daily at the Disney Studios over near the Lights Motor Action stunt show. (Check a times guide or ask a Cast Member when they're expected to be out.)
Darth Vader and a couple of storm troopers are often out near the Star Tours ride. We saw them there in June and not during a Star Wars Weekend.
By the way (or should that be BTW
), you can see a list of frequently used shorthand/acronyms here:
PassPorter Community - Message Boards and Forums - FAQ: Reading and Posting Messages
Hope you find the characters you're looking for!
Eileen