Right before Toby comes into the cafeteria, when Mona is sitting with Hanna and Spencer, Hanna sets her lip-gloss on the table, standing up. In the next shot, it is flat on the table.
When Aria walks into the dance she has a black glove only on her left hand. You can see in the frame from behind and then again in the frame where she's standing at the top of the staircase. But the next angle shows her stepping off the stairs and the glove is gone.
When [presumably] "A" paints over the 8 at the end of the episode, it's is painted blue then immediately painted white, but the paint somehow doesn't mix.