For the past two years that we've been, Baloo and King Louis have scarves on, Pluto has a scarf and Goofy was in a Santa suit. Mickey and Minnie wear adorable sweaters for their meet and greet. Not quite as elaborate as other parks' character costumes, but still fun!!
Also, depending on when you're going, check the resort schedules - the week before Christmas characters sometimes appear in certain resort lobbies - two years ago we met Mickey and Minnie in awesome turquoise snowflake outfits we'd never seen before at the Beach Club. We were staying at Boardwalk and they were wearing the same outfits as AK there, so we were excited to see something different at Beach Club.