Continuity mistake: When Charlotte hastily makes the bed and shoves Ted out onto the window ledge, the bed covers rearrange themselves between shots: a purple sheet that she'd tucked in before is now peeking out over the bedspread. (00:15:05)
Revealing mistake: The seen where Teddy is standing in rain talking to Charlotte in her car you can see how the rain followed his movement. There is a thicker spout of water dripping and you can see the outline of it.