Continuity mistake: When the gang are at Grace's mothers, Karen takes her pill whilst holding the bottle. In the next shot the bottle is out of her hand, on the side, and the cup she was holding has swapped hands.
Continuity mistake: After Jack tells Mrs. Adler that Nathan dumped Grace, she walks over to Grace. Grace is holding a plate of finger foods, with sticks in them. The sticks and food change position between shots.