When Stanley comes back from taking Stella to the hospital, he is looking for a bottle opener. He finds it on the mantelpiece, shakes up a bottle of beer, and opens it. The beer foams up and spills on his trousers. But if you watch at the moment when he swings himself up to sit on the table - before he opens the bottle - you can see that the front of his trousers are already wet. Apparently they re-shot it without him changing into dry trousers.
During the conversation about the Napoleonic Code between Stella and Stanley, the plate Stanley has been eating off of disappears off of the top of the trunk, which is suddenly open.
Just after Stanley goes through Blanche's things, his shirt goes from fairly dry, to two distinct spots on his chest, to soaked all the way down the front, in a matter of seconds.
The position of the collar on Stanley's silk pajamas changes between shots, varying between up and down.
When Mitch embraces Blanche, she puts her arm around his shoulders, which changes between shots, either her left one or her right one.
When Stanley is about to give Blanche the birthday "gift" of a ticket back home Marlon Brando opens the wallet to discover that the envelope with the ticket it missing. There is a sharp edit and then the scene continues with the wallet missing from Stanley's hand and replaced with the envelope containing the ticket.
Stanley says he served in the 241st Engineers and fought in the Battle of Salerno. However the 241st Engineer Combat Battalion fought in the Asiatic-Pacific Area, not in Europe.
Stanley says that Louisiana utilizes the Napoleonic Code (which was promulgated a year after the Louisiana Purchase). Actually, Louisiana uses as its private law the Louisiana Civil Code. Although it is similar to the Napoleonic Code, it has always been the controlling legal authority in the state.
When Stanley and his friend bring Blanche's trunk into the apartment, Stella hides behind a curtain because she is not yet dressed and wearing her slip. Yet as soon as Blanche asks her to retrieve her "blue net," she loses her modesty and walks freely in front of the same guy she had just hidden herself from.
Blanche and Stella are sisters, yet Blanche speaks with a deep Southern accent and Stella does not.