Shaw, Pushkin & Melville : freely mixing fact and fiction

While novelists Melville (Moby Dick) and Pushkin (Eugene Onegin) are well known for mixing fact and non fiction in very close quarters, we don't usually accept that almost all playwrights do much the same.

George Bernard Shaw is very much the best known playwright in this regard.

That is because Shaw's (nominally non fictional) prefaces and stage directions describing the fictional characters' lives and the play's fictional locales were all very much longer than the scripts of his fictional plays.