There is a new event coming to Japan for a tie-in to the two movies this summer.
There is one event Pokemon each for the two movies, which are each from characters from the different versions of the movie.
The event will run:
from June 17th to July 7th at McDonald's restaurants,
then
from July 8th to September 8th over Nintendo Wi-fi.
If you have Black, you get a shiny Hydreigon (from the character, Carita).
If you have White, you get a shiny Golurk (from the character, Janta).
Original Source: flyer from a McD's, posted on twitter
http://twitpic.com/56vol1
Official Site:
http://www.pokemon-sp.jp/news-sp/2011/06/0607_01.html?SP-inc=hotnewsbox
Official Site update:
http://www.pokemon-sp.jp/news-sp/2011/06/0615_02.html?SP-inc=hotnewsbox
Golurk:
Level 70
OT: ジャンタ (Janta) 06171
Iron Fist
Shadow Punch, Hyper Beam, Gyro Ball, Hammer Arm
Cherish Ball, Wish Ribbon
Hydreigon:
Level 70
OT: カリータ (Karita) 06171
Levitate
Hyper Voice, Dragonbreath, Flamethrower, Focus Blast
Cherish Ball, Wish Ribbon
(I'll be able to pick both of these up on my way home from work on the 17th, for any who are wondering)