When Randy is "playing" on his Xbox 360, there are no working control pads connected to it. There are no wired controllers plugged in to it, and if he is using a wireless controller, the controller light on the front of the Xbox should be on. It isn't.
The goof item below may give away important plot points.
In the scene when Wilson Jr goes to see the man to see why he wants to kill his mother when he walks in the the office his shoes are royal blue air force ones. After they carry him out the office his shoes are light blue air force ones.