Big Al appears in the Frontierland Hoedown at the Magic Kingdom and randomly at Epcot.
Abu doesn’t offer regular meet and greets. He does appear for Mickey’s Not So Scary Halloween Party and Mickey’s Very Merry Christmas Party. You can see him in the Magic Kingdom daytime parade.
Beginning December 11th (changed from December 4th) the characters from UP! (Russell and Dug) are said to be coming to Animal Kingdom and will be meeting near the Flame Tree BBQ.