Here's a recent thread on characters:
http://www.disboards.com/showthread.php?t=2448444
We've seen tons of characters on our trips. Many of them are at pre-arranged places at pre-arranged times, and some of this information is available on the daily schedule or at City Hall or at Guest Relations at DCA or at the info booth in either park.
We've commonly seen (not all on the same trip) Mickey, Minnie, Donald, Daisy, Goofy, Pluto, Chip and Dale, Lilo, Stitch, Alice, The Queen of Hearts, Mad Hatter, Peter Pan, Captain Hook, Cruella, Buzz, Woody, Jesse, Brer Bear, Pooh, Tigger, Eeyore, Sully from Monsters Inc., Mr. and Mrs. Incredible, and Frozone.
Some of our more special finds have been Tweedle Dee and Tweedle Dum, Rabbit from Winnie the Pooh, and Beast.
Movie or video releases sometimes bring out special characters. We saw Dopey that way. DS8 is for some reason a huge Dopey fan.
DSs aren't into princesses so we've never bothered. We see them out occasionally, but I think they're mostly at the Princess Fantasy Fair.
Villains galore show up at Halloween time.
