Continuity mistake: In Kris's room, when she and Jesse find out they dream of Freddy, a turquoise coloured blouse on the right disappears.
Continuity mistake: At the diner, after the girl asks Dean "What's going on?", the camera shows Quentin drinking and then taking the glass away from his mouth. A frame later from a different shot he's sipping and removing the glass again.
Continuity mistake: At the diner, after Jessie leaves, Nancy arrives and asks what's going on while raising her right arm. A frame later the arm is lowered.
Chosen answer: They were upset because they realise that Freddy is coming to get revenge on them for his death.