Name the names: stage & real

"John Garfield was born Jacob Julius Garfinkle on the Lower East Side of New York City, to Hannah Basia (Margolis) and David Garfinkle, who were Jewish immigrants from Zhytomyr (now in Ukraine). Jules was raised by his father, a clothes presser and part-time cantor, after his mother's death in 1920, when he was 7. He was sent to a special school for problem children, where he was introduced to boxing and drama. He won a scholarship to Maria Ouspenskaya's drama school. He joined the Civic Repertory Theatre in 1932, changing his name to John Garfield and making his Broadway debut in that company's Counsellor-at-Law. Joined the Group Theatre company, winning acclaim for his role in Awake and Sing. Embittered over being passed over for the lead in Golden Boy, which was written for him, he signed a contract with Warner Brothers, who changed his name to John Garfield."

But Why ? .... 

Because sometimes the Screen Actor's Guild or Equity rules require a name change

"Like other organizations that represent actors, SAG rules stipulated that no two members could have identical working names; many actors were thus prevented from registering under their own names and had to make changes. Some maintained their usual name but added a middle initial; others adopted a stage name quite different from their legal name to comply with this rule. Notable examples include Michael Keaton, Michael J. Fox and Emma Stone, whose birth names "Michael Douglas", "Michael Fox" and "Emily Stone", respectively, had already been registered by other actors."

and sometimes names are changed for other reasons, such as Family connection:
Actor Nicolas Cage, born Nicolas Coppola, adopted a stage name to avoid comparisons with his uncle, director Francis Ford Coppola.
Some individuals who are related to a celebrity take a different last name, so they are not perceived to have received undue advantage from their family connection.

More from wiki here:

Tony Randall was born Aryeh Leonard Rosenberg; he had a sister named Edna. When he co-starred on the TV sitcom The Odd Couple, his character, Felix Unger, had two children named Leonard and Edna after himself and his sibling.

Natalie Zacharenko

Amos Muzyad Yaqoob Kairouz
In 1932, he began performing on radio in Detroit at WMBC on The Happy Hour Club and  performed as "Amos Jacobs Kairouz".

In 1940, after he moved to Chicago, he did not want his friends and family to know he had gone back into working clubs where the salary was better, so he came up with the pseudonym "Danny Thomas" (after two of his brothers).

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His Brother, Thomas Yakhoob became Tom Jacobs and appeared as a bit player on shows produced by his  brother.

Suzanne Lorraine Burce



Jane Powell with Husband Dickie Moore (John Richard Moore Jr.)