When Jim Carrey is impersonating, it's clear that it's Jim Carrey impersonating someone for comedy-sake, not providing a service in lieu of someone else. In other words, Jim Carrey isn't getting paid to stand in for Jack Nicholson for example. Otherwise, it looks more like the Midler vs Ford Motor Co. case[1]
[1] https://en.wikipedia.org/wiki/Midler_v._Ford_Motor_Co.