The Osborne Spectacle of Lights at MGM is a must.
There's also the Candlelight Ceremony at Epcot as well as their Christmas around the World festivities in which each country presents a culture oriented Christmas presentation.
MGM also has their motorcars parade which is made "Christmasy."
AK also has the Jingle Jungle Parade.
ETA: Just realized you said MK. Oops!