explains the requirement here, and provides other details on registering performing artist names. Also, you cannot register the name of a living person without their consent so you will need an affidavit for that purpose. (Here's an article we wrote about registering family names).
Do you need to register your name? Many actors have acquired trademark protection for entertainment services -- for example, Robin Williams, Clint Eastwood, Meg Ryan and Sandra Bullock. But the vast majority of actors don't register their names as trademarks (including Tom Cruise, Julia Roberts, and Dustin Hoffman) because there's usually little need for trademark rights for movie actors unless they are offering a non-entertainment business such as a line of perfume or fish and chips. In addition, you don't need to worry about someone else registering your name. Living persons must consent to use of their name, so for example, the USPTO routinely prevents registration of well-known celebrities by profiteers seeking to cash in. Typically, actors find reasonable protection via actor's unions -- for example, one goal of the Screen Actor's Guild, (SAG) is to steer new registrants away from using any names that appear in their database (including derivatives, for example "Tommy Cruise").