Background: The Screen Actors Guild (SAG) was an American labor union which represented over 100,000 film and television principal and background performers worldwide. On March 30, 2012, the union leadership announced that the SAG membership voted to merge with the American Federation of Television and Radio Artists (AFTRA) to create SAG-AFTRA. According to SAG's Mission Statement, the Guild sought to: negotiate and enforce collective bargaining agreements that establish equitable levels of compensation, benefits, and working conditions for its performers; collect compensation for exploitation of recorded performances by its members, and provide protection against unauthorized use of those performances; and preserve and expand work opportunities for its members. The Guild was founded in 1933 in an effort to eliminate exploitation of Hollywood actors who were being forced into oppressive multi-year contracts with the major movie studios that did not include restrictions on work hours or minimum rest periods, and often had clauses that automatically renewed at the studios' discretion.
Context: In 1925, the Masquers Club was formed by actors discontent with the grueling work hours at the Hollywood studios. This was one of the major concerns which led to the creation of the Screen Actors Guild in 1933. Another was that the Academy of Motion Picture Arts and Sciences, which at that time arbitrated between the producers and actors on contract disputes, had a membership policy which was by invitation only. A meeting in March 1933 of six actors (Berton Churchill, Charles Miller, Grant Mitchell, Ralph Morgan, Alden Gay, and Kenneth Thomson) led to the guild's foundation. Three months later, three of the six and eighteen others became the guild's first officers and board of directors: Ralph Morgan (its first president), Alden Gay, Kenneth Thomson, Alan Mowbray (who personally funded the organization when it was first founded), Leon Ames, Tyler Brooke, Clay Clement, James Gleason, Lucile Webster Gleason, Boris Karloff, Claude King, Noel Madison, Reginald Mason, Bradley Page, Willard Robertson, Ivan Simpson, C. Aubrey Smith, Charles Starrett, Richard Tucker, Arthur Vinton, Morgan Wallace and Lyle Talbot. Many high-profile actors refused to join SAG initially. This changed when the producers made an agreement amongst themselves not to bid competitively for talent. A pivotal meeting, at the home of Frank Morgan (Ralph's brother, who played the title role in The Wizard of Oz), was what gave SAG its critical mass. Prompted by Eddie Cantor's insistence, at that meeting, that any response to that producer's agreement help all actors, not just the already established ones, it took only three weeks for SAG membership to go from around 80 members to more than 4,000. Cantor's participation was critical, particularly because of his friendship with the recently elected President Franklin D. Roosevelt. After several years and the passage of the National Labor Relations Act, the producers agreed to negotiate with SAG in 1937. Actors known for their early support of SAG (besides the founders) include Edward Arnold, Humphrey Bogart, James Cagney, Dudley Digges, Porter Hall, Paul Harvey, Jean Hersholt, Russell Hicks, Murray Kinnell, Gene Lockhart, Bela Lugosi, David Manners, Fredric March, Adolphe Menjou, Chester Morris, Jean Muir, George Murphy, Erin O'Brien-Moore, Irving Pichel, Dick Powell, Edward G. Robinson, Edwin Stanley, Gloria Stuart, Lyle Talbot, Franchot Tone, Warren William, and Robert Young. CANNOTANSWER
Question: Who was Frank Morgan?

Answer:

Ralph's brother, who played the title role in The Wizard of Oz), was what gave SAG its critical mass.