Discussed a lot in the last thread on the issue, but, yes, imitation of celebrity voices voices for commercial purposes can violate the right of publicity (also known as the right of personality) in many US jurisdictions, including California (this is a matter of state statute and/or common law, not federal law.)
Worth pointing out that this doesn't really do the same thing. Some percentage of the time it will be detected by some of your customers and it won't work the same for them.
It's not just about seeing a celeb face. There's more going on that was discovered in the 80's and 90's, I think (that's when it became a big thing at least).
Built into it is the implication that the celeb likes the product. Additionally, products and branding have become a part of our personalities (IMO bad trend). So in a way you can BE like the celeb.
You will be just as cool as michael jackson if you just hold a pepsi in your hand. Sure, none of us really think this at face value, however it's implied and hinted at.
Kind of, not in that there is a binary “celebrity/not-celebrity” divide, but the interest protected and the potential for damages from violating them are associated with the kind of public commercial exposure that is associated with celebrity.
So if you hire a voice actor that naturally sounds like a celebrity then you should be safe from any legal action. Otherwise they could sue each other.
Look up the concept of mens rea - the intent matters. If you hire somebody because you want a look/voice-alike that is legally distinct from hiring somebody who happens to have a certain voice.
