To retarget from one character to another:
Create an HIK character definition for each character.
From the Character Controls window > Character drop-down list, select the target character.
From the Character Controls window > Source drop-down list, select the name of your source character. (All HIK characters available in the scene are automatically listed in this drop-down list.)
Select > Edit > Controls > Retarget.
The Retargeting Options dialog box appears, where you can choose to activate or disable any options.
The keyframe animation from the source character is copied to the target character, and MotionBuilder makes the necessary adjustments for any differences in the size and shape of the two characters. The exact dynamic of your original keyframe animation is preserved on the target character.
If the Constrain References property for one of the characters is active, a Character dialog box appears asking if you want to disable the Constrain References property.