Continuity: The window after Stanley throws the radio through it.
Continuity: When Mitch embraces Blanche, she puts her arm around his shoulders, which changes between shots, either her left one or her right one.
Continuity: When Stan comes back from taking Stella to the hospital, he is looking for a bottle opener. He finds it on the mantlepiece 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.
Errors made by characters (possibly deliberate errors by the filmmakers): 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.
Continuity: During conversation about Napoleonic Code between Stella and Stanley, plate Stanley has been eating off disappears off top of trunk which is suddenly open.