Santa- I really like the idea of Jack Nicholson or Christopher Walken.
Mrs. Claus- Drew Barrymore (why not?)
Rudolph- Santa's Little Helper from The Simpsons
FBI Leader- Ben Stiller
The Sniper- Jack Black
Virginia- Dakota Fanning
Little Friend- Jonathan Lipnicki (he can still pull off 5-10 years old)
Eyewitness News Reporter- Jim Carrey (from Bruce Almighty)
Helecopter Pilot- Al (guest apperance)
Elfs- Prince, Gary Coleman, and a random assortment of other midgits.