I think that the previous post was very well spoken and strong in the analysis featured. I would only echo that the idea of appearance vs. reality is a driving element throughout the play. Characters are constantly battling between appearances and the underlying truth beneath it. When Stella agrees to sign the commitment papers for Blanche, she does so under the guise that it is "the right thing to do." This appearance is something that she, herself, repudiates with her line, "What have I done?" As previously stated, Blanche lives with the dichotomy between appearance and reality. It is her home, where she resides. When she says, "I have always depended on the kindness of strangers," it is a line that reflects this home between the two worlds. The appearance of her belief in people is undercut by the harsh treatment she both gives and receives to them. The appearance of strangers being kind and benevolent is also contradicted with the people that Blanche interacts with in the drama, individuals who don't really possess much in way of kindness to Blanche. While the statement also shows a benevolence, Blanche is capable of cruelty and malice, elements that she, even with her apparent skills of self reflection, might not be able to recognize in her own actions. Finally, I would think that the marriage between Stella and Stanley might be one other example of this idea of appearances and reality. I think that one of the fundamental messages of the play regarding marriage is how the collapse of traditional roles might allow for abuse and the pretense for it to take place in the realm of the private. Blanche recognizes that what Stella might take for passion and brooding intensity might just be good, old fashioned abuse. The appearance that one perceives is cast by the reality the other reads.
The theme of appearance vs. reality in Streetcar Named Desire is most obviously seen in the character of Blanche.
Blanche tries to give off the appearance and maintain a reputation of being genteel, proper, reserved, educated, and sophisticated. She tries to appear as a person from the Old South.
In reality, she sneaks drinks every chance she gets, tries to seduce a boy when she finds herself alone with him, flirts with Stanley, and has a secret past that finally gets revealed.
This is not to say that Blanche is not at all sympathetic. She is, at least in some ways, in a no-win situation. The economy in the South was destroyed by the Civil War, and numerous plantation owners (as Blanche's family was) never recovered. As she says in the final scene, she has always had to depend on the kindness of strangers--specifically, men.
Perhaps the most moving example of appearance not meshing with reality is the reversal in the final scene. Blanche actually tells the truth about being raped by Stanley, while Stanley lies. Blanche's means of coping is to hold on to the hope that her old friend is coming to rescue her, a hope everyone, both the other characters and the audience, knows is false.