“If a farmer calls me to a sick animal, he couldn't care less if I were George Bernard Shaw.”

Hello Out There (1941)

Act III
1910s, The Doctor's Dilemma (1911)

Source: David and Goliath: Underdogs, Misfits, and the Art of Battling Giants

In the The Bicycle Rider In Beverly Hills (1952) Saroyan additionally wrote of Shaw:
He was a gentle, delicate, kind, little man who had established a pose, and then lived it so steadily and effectively that the pose had become real. Like myself, his nature has been obviously a deeply troubled one in the beginning. He had been a man who had seen the futility, meaninglessness and sorrow of life but had permitted himself to thrust aside these feelings and to perform another George Bernard Shaw, which is art and proper.
Hello Out There (1941)

Hello Out There (1941)
Context: I have read books about the behavior of mobs — The Mob by Le Bon, if I remember rightly, was one — about the crime in children, and the genius in them, about the greatest bodies of things, and about the littlest of them. I have been fascinated by it all, grateful for it all, grateful for the sheer majesty of the existence of ideas, stories, fables, and paper and ink and print and books to hold them all together for a man to take aside and examine alone. But the man I liked most and the man who seemed to remind me of myself — of what I really was and would surely become — was George Bernard Shaw.

Source: The Confessions of Aleister Crowley (1929), Ch. 7.
Context: My mother was naturally a rather sensual type of woman and there is not doubt that sexual repression had driven her as nearly as possible to the borders of insanity.
My cousin Agnes had a house in Dorset Square. My mother took me to tea there one afternoon. A copy of Dr. Pascal was in the room. The word "Zola" caught my mother's eye and she made a verbal assault of hysterical fury upon her hostess. Both women shouted and screamed at each other simultaneously, amid floods of tears. Needless to say, my mother had never read a line of Zola — the name was simply a red rag to a cow.
This inconsistency, by the way, seems universal. I have known a printer object to set up "We gave them hell and Tommy", while passing unquestioned all sorts of things to which exception could quite reasonably be taken by narrow-minden imbeciles. The censor habitually passes what I, who am no puritan, consider nauseating filth, while refusing to license Oedipus Rex, which we are compelled to assimilate at school. The country is flooded with the nasty pornography of women writers, while there is an outcry against epoch-making masterpieces of philosophy like Jurgen. The salacious musical comedy goes its libidinous way rejoicing, while Ibsen and Bernard Shaw are on the black list. The fact is, of course, that the puritan has been turned by sexual repression into a sexual pervert and degenerate, so that he is insane on the subject.

Interview in The Vegetarians by Rynn Berry (Brookline, MA: Autumn Press, 1979), p. 30.

Version given in Irrepressible Churchill: A Treasury of Winston Churchill’s Wit by Kay Halle, 1966
Apocryphal, originally featured Noël Coward and Randolph Churchill (Winston’s son); attested 1946 (columnist Walter Winchell, attributed to anonymous United Press journalist in London). Originally only featured first half about lack of friend; second half (retort about lack of second performance) attested 1948, as was replacement of personages by George Bernard Shaw and Winston Churchill. Specific plays added in later variants, ranging from Man and Superman (1903) to Saint Joan (1923), and appeared in biographies and quote collections from the 1960s.
The quote is presumably apocryphal due to earliest attestations being too different, less famous personages (easily replaced by more famous ones), the quotation becoming more elaborate in later versions, the 20+ year gap between putative utterance and first attestation, and the approximately 50 year gap between putative utterance and appearance in reference works, all as undocumented hearsay.
Detailed discussion at “ Here are Two Tickets for the Opening of My Play. Bring a Friend—If You Have One http://quoteinvestigator.com/2012/03/25/two-tickets-shaw/”, Garson O’Toole, Quote Investigator http://quoteinvestigator.com/, March 25, 2012.
Misattributed