Continuity mistake: When Mrs. Hastings is on the phone abut the tree in the garden, her phone is not in call mode.
Continuity mistake: When Lieutenant Tanner has all the Liars lined up at the station, she says that she's giving them a chance to tell their side of the story before her side becomes the only side. As she says this, Aria can be seen scratching her head in the reflection behind Tanner. In the next shot however, both Aria's arms are suddenly folded.