When Michael meets Kim at the open air terrace, her hair is slightly wavy and dry. When she gets in the car with him her hair is smooth,glossy and poker straight.
When the RV pulls over to drop Chris off by the side of the road, the left-hand turn signal comes on, but as the RV is pulling away, the right-hand turn signal is now on.
Near the end of the movie when Casey Affleck is standing at the door to pick up his kid, the strap of his bag changes from normal to upside down.
When Casey Affleck is hiding in the bathroom from his wife and crying baby, he reaches to open the door with his left hand, thus pulling on the door it should open from the left, yet the camera cuts and the door opens from the right without switching places.
They find out the sex of the baby. Shortly after, she announces she is 3 months. Normally, you cannot find out the sex of the baby until 20 weeks, 5 months.
When Michael comes home after the party with Kim and gets into a fight with Jenna, when she asks him "what will happen 10 years from now?" she speaks with her Australian accent.