When Big Daddy announces the engagement and Blanche goes to hug him, his hat switches hands between shots.
Dorothy takes a cheesecake out of the fridge and it's halfway gone. When she gets to the table, the cheesecake changes and has not had a piece cut out of it. When she sets it on the table, it is halfway gone again.
When Blanche asks Dorothy and Rose to perform the song "Miami", a microphone can be seen above her.
Rose's incorrect usage of the word "thrice" is not an error at all. It is a perfect illustration of Rose, the character.
"Thrice" is a real word, but it means "to do something three times," not "three of them" as Rose uses it.