People assign labels to other humans to help organize and personalize everyday life. Recent studies even show that we are not the only species on this planet to do so. Marmoset monkeys, bottlenose dolphins, and African elephants act in a similar manner. Things get hairy, though, when names are similar.

In Hollywood, the Screen Actors Guild (SAG) has long encouraged new members to avoid using the same name as a current member. The union, now SAG-AFTRA, even warns against using a name that is too similar for both the sake of clarity and brand recognition as well as legal liability.

Because the roster of members changes daily, SAG doesn’t check it until a performer is ready to join. During that process, an Alternate Professional Name Form is filled out, which asks for three possible stage names. Once the initiation fee clears, a final name check is performed.

Performers can choose to ignore SAG’s warnings.

“While we strongly discourage members from selecting a professional name that is in conflict with a current member, SAG-AFTRA cannot preclude a member from using their legal name as their professional name,” SAG-AFTRA spokesperson Pamela Greenwalt explained. “When such a situation arises, SAG-AFTRA requires that the applicant/member sign an ‘Acknowledgement’ form in order for their request to be processed.”

The majority of members do heed SAG’s advice—which makes sense. Performers are essentially a branded product in human form, and a confused mind doesn’t buy. As an entertainer, you want to be remembered.

Let’s take a look at some other name guidelines and actors who have changed their monikers because of the SAG preference:

What’s in a name for Michael Keaton?

The one-name, one-actor preference is not the only name rule in the union. When a performer dies, their moniker is held unassigned for three years starting on the date of their passing. If a current member changes their name, their old one stays unassigned for three years. If a member is kicked out of the union, their name is immediately available. If a member honorably withdraws or owes membership dues, their name is held for five years.

SAG’s rules around naming recently came into the spotlight thanks to Beetlejuice Beetlejuice star Michael Keaton.

Keaton was born Michael Douglas on September 5, 1951. He grew up the youngest of seven in a Pittsburgh suburb. When he was trying to make a go at acting in the 1970s, there were two other competitors. There was Kirk Douglas’s son Michael Douglas and a talkshow host named Mike Douglas. A quick look in the phone book inspired his new last name, Keaton, which proved to serve the man well.

Keaton’s breakout role came in the 1979 CBS sitcom Working Stiffs. And he would cement his comedic standing in films such as Night Shift and Mr. Mom and achieve superstardom with Beetlejuice and Batman.

These days, Keaton is changing his name again. He wants to be known as Michael Keaton Douglas from now on, as recently reported by People magazine, a hybrid of his stage and real names. It’s safe to say that he is certainly well-established enough now to avoid confusion.

Julianne Moore

Julianne Moore also had to use a stage name when joining a union (in this case, Actors’ Equity, the union for stage actors) and wasn’t too happy about it. She was born Julie Anne Smith. She looked to other family members’ monikers for inspiration. 

“My father’s middle name is Moore; my mother’s name is Anne. So I just slammed the Anne onto the Julie,” she explained to the New York Times in 2001. “That way I could use both of their names and not hurt anyone’s feelings. . . . But it’s horrible to change your name. I’d been Julie Smith my whole life, and I didn’t want to change it.”

Emma Stone

Emily Jean Stone also found herself in this same situation when she was 16 years old, as she explained to W Magazine. She first tried out the name Riley, but she kept forgetting to answer to it on set. She finally landed on Emma because it sounds similar to Emily. She told W that her good friends normally call her “Em” anyway, so it worked out.

Diane Keaton

No, Diane and Michael are not related. They are simply both victims of the SAG policy. Diane’s actual legal surname is Hall, just like her iconic character in the movie, Annie Hall. She changed it when joining the union.

Michael J. Fox

Michael kept the majority of his real name but had to add the middle letter. (As his Foundation explains, there was already a “Michael Fox” in SAG.) His given name is Michael Andrew Fox but he chose to go with Michael J. Fox professionally to honor fellow actor Michael J. Pollard.