Euron says that he, Yara and Theon are the last Greyjoys left in the world. There is a fourth Greyjoy - Aeron, Euron's brother.
Qyburn tells Bronn "The queen's brothers made promises to you and broke them." Tyrion has never broken any promise he made to Bronn.
Sophie Turner is very visibly wearing a wig for the first time throughout the show in Season 8; her hairline is a different shape and her hair is a darker shade of red than it was previously.
Arya asks Jon "How did you survive a knife through the heart?" No one has ever told Arya about the assassination of Jon.