Continuity mistake: After the Robert Redford clip, when it cuts to the Griffins walking toward Doug's house, in this exterior shot (and a previous exterior shot) the front door is located between one window and the garage, but in the following interior shots there's a window on both the left and right side of the front door. (00:14:20)
Other mistake: The guys lasso the bear. Then Peter impossibly lassos the bear's legs. There's no way for the lasso to go around the bear's leg with his feet on the ground. And the lasso couldn't have gone over the body down to the legs since the other ropes would have gotten in the way.