Continuity mistake: When Peter starts grabbing himself, his shirt is seen semi-tucked into his pants. The camera angle changes and the left side of his shirt is now hanging outside of his pants. (00:55:34)
Visible crew/equipment: When Peter is at the golf course with Mrs. Arness, you can see the golf cart behind them. In the next scene, there is a woman sitting in it and she appears to be the stand in for Mrs. Arness. (Confirmed on the audio commentary). (00:40:05)
Continuity mistake: At the end of the movie in the scene where they are moving into the new office, Peter is talking to Charlene at his desk. Behind her there are three books stacked in a certain order. Later in the scene when he is talking to his wife the books are stacked differently. (01:37:40 - 01:38:45)
Answer: It's called "Way of Life" by Lil' Wayne with Big Tymers and T.Q.