Mariah Carey -- Flash in the Pan for Game of War Commercial (VIDEO)

Mariah Carey's Game of War commercial is in the can, and we got hold of it ... watch carefully, because if you blink twice you'll miss her.

Mariah shows up on camera for 2 seconds during the 1 min promo. They replay 6 words from her monster hit "Hero" 3 times ... and then it's over.

She looks good, and she had a tough act to follow.