When Rachel and Sam visit their former country cottage she at first says they have never been back since his disappearance, but later Sam asks her if she and Joe have been there and she says they have.
When Tony is made to put Harry (the Ribbon snake) away, there appear to be eggs in the tank. Ribbon, or Garter snakes give live birth with no external eggs.
When Tony beats Sam at Connect 4, playing red, there are already two different victories for yellow visible.
In the prologue, Tony and Sam are seen together before Sam's abduction. The movie then fast forwards to three years later. Despite this, Tony doesn't seem to have aged at all but since the prologue is a dream of Tony's, he can have the same age in the dream and in real life, even if three years have passed since the events shown in the dream.