Definitely check out the new Disneyland app - it seems to actually be listing characters that are actually there at that time! Besides the normal fab 5 in their 20s attire (which is absolutely adorable - I'd seriously suggest you go see them!), DCA also has Buzz/Woody/Jesse back in Paradise Pier, some Disney Junior characters near where Anna & Elsa meet (Jake, Sofia, Dr. McStuffins) and Sully and some of the Incredibles a little farther into Hollywoodland. You can also meet Lightning McQueen, Mater, and Red the fire truck in Cars land.
The Mad Hatter and Alice meet in Disneyland, usually near the tea cups is where we've seen them. The Mad Hatter is absolutely hilarious! Plus there's Alice and Peter Pan, Mary Poppins and Bert, and some Stormtroopers. Those ones don't usually seem to form lines but are rather just kinda walking around.