Some questions you could consider investigating would be: do the characters grow at all from the beginning of the play to the end? Is what happens between Blanche and Stanley inevitably surprising or surprisingly inevitable? Is Blanche or Stella the more delusional character in this play? It is important to recognize the ambiguity of the ending with A Streetcar Named Desire. Censorship was a major issue back then so when they made the movie version of the play, the director was basically forced to create an ending that would make it feel as though good had won out over evil. You could possibly write about the different endings of the play and the movie and discuss the effect that has on the audience's opinions of the characters. Another interesting question, is true tragedy always inevitable or often is it a tragedy of small mistakes that lead to a major downfall?