Continuity mistake: When Dean goes to the hospital, the police officer hands him a large manilla envelope containing the photos of Annie/Joanna. Dean folds the envelope in half, pressing it together firmly, then shoves it into a jacket pocket. Later, when Dean gives the photos to Billy, the envelope is flat and the pictures are in mint condition - no bends or wrinkles.
Other mistake: During the opening of the mini golf course you see in one shot that the ball comes out of Lincoln's mouth. Ever notice that there is no where for the ball to go? No artificial putting green is there, just a wooden platform and natural grass.
Continuity mistake: When Dean is picking up Annie at the hospital he goes through some photos. When he picks them up you see a picture of Annie. In the next shot on the table when he throws them down to look at her the first one on the stack was the second or third on the stack before.
Continuity mistake: When Annie goes to pick up the boys at school and they have poison oak, there is a shot of Annie holding her purse. Then they show her from behind with her purse over her shoulder, and then from the front again holding it.