> BTW: the size of the encrypted file on the Nintendo server will probably give it away (if under 9KB it is not DLC).
Update: the Japanese giveaway is on their servers now. Too small to contain DLC.

For example, the data sizes for the encrypted files:
Original Japanese giveaway (red Pikmin hat + letter in Japanese) - 9K bytes
Current EU/UK/OZ giveaway (red Pikmin hat + letters in several languages) - 12K bytes
Current Japanese giveaway (Feb 14) - 1K bytes