Wednesday accidentally says "Tyler warned me that something bad was coming" when it wasn't Tyler. It was Rowan. (39:42)
Tyler's prison van is travelling in the wrong direction at the end. Both him and the Addams family are leaving Nevermore but they pass each other travelling in opposite directions.
Near the end, in Weems' office, a crew member can be seen reflected in the mirror at the far end of the room on the left-hand side of the screen.
After the meeting in the Nightshade library, Enid is surprised when the Nightshades (including Thing) all perform the "secret snap." Ajax would have had to have performed the snap to get her into the library through the secret entrance.