Continuity mistake: During the sales trip the two main characters stop at a gas station to get gas. during this stop Tommy bends the door back and after some struggle gets it to the normal door position. Before Richard gets back to the car however there is a shot of the door all dented up but in place. When Richard pulls the door off it falls to the ground and there isn't a single dent on it. (Also, is it me or does it seem a little ridiculous that someone that loves his car so much didn't notice the large dent down the edge of the door as he faced it while walking from the station to the car?)
Continuity mistake: The deer knocks the rear-view mirror off the windshield, however, when the boys are driving down the highway and the car hood flies off, you can see the mirror again, then it's gone and then it's back again.
Continuity mistake: In the scene where Tommy and his 'girlfriend' are sitting in the boat and about to get picked on by the kids on the shore, Tommy's Life jacket changes. One shot it's got a white line and a button on it and in the next shot, they're not there. Then the line and button show up again.
Character mistake: When Tommy is being shown his new office the glass reads "Thomas R. Callahan III, " but when Tommy is introduced as the new President of the company he is introduced as "Tom Callahan, Jr." which would be his dad. (00:11:35 - 02:11:55)
Factual error: When the two are travelling the country to sell the brake pads, when they go to Detroit, it is not Detroit. The Detroit skyline looks nothing like that and the Detroit road sign appears to be added/airbrushed in.