Ask HN: Google request permission for using likeness of celebrity in Doodle?

Does Google request permission for using the likeness of a celebrity in a Doodle? I'm curious to know because they incorporate the brand of the celebrity into the Google logo. How do they know if the person they are using would give permission to be associated with the Google logo? This looks like an intellectual property problem to me. For instance, I doubt that Google will let me use their logo in association with other brands. Any thoughts?