Same as with the Black sheep Trophy, you will be putting an animal in a pile of ash. In Chapter one where you will have the little brother run on the wheel to lower the bridge, at the lower part of the screen theres another path, there you'll see 5 bunnies 4 black and 1 white. take the white bunny with whichever brother you want and drop it in the pile of ash. This will turn the bunny black, and then the Trophy is yours.