Impersonation of celebrities for commercial purposes falls under the celebrity's right of publicity. In general, any person has the right to prevent his/her image/likeness/voice from being used by someone else for commercial purposes. However, publicity rights are different in every state and what may be permissible in one state may not be permissible in another. For example, the rights vary from state to state depending on whether the celebrity is living or deceased. You need to consult someone who knows the laws governing the right of publicity in the state(s) that you will be performing.
Answered on Jun 02nd, 2012 at 12:57 PM