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 they get on the flight to Chicago, it's an American Airlines 747. No airline in America would fly a 747 from Ohio to Chicago, a 1 hour or so flight. No one would waste the amount of fuel and costs to fly a plane that big full of passengers for such a short flight.
Visible crew/equipment: Filming equipment is reflected in the window of a passing car in the scene where Tommy is relieving himself on the side of the road.
Deliberate mistake: Why would Richard, big Tom's 'right hand man,' have to drive his cherished vintage car on a business trip that would take him hundreds, if not a thousand miles? He surely could have taken a company vehicle. Of course, then they couldn't do the 'car slowly and humorously being destroyed' shtick.
Continuity mistake: Right before they hit the deer, the car's windshield is gone. After they hit the deer, it has returned.
Suggested correction: It is possible (probably not common) to be a "III" and a "Jr." If you are named after your father, and he is still alive you are a Junior. If you both share the name with another member up the family tree say your great grandfather, then your father would be a "II" and you would be a "III." But since your father is still alive, you can still go by junior. I've known one person in this situation.
I guess you missed the part of the movie where his father died. He's made the new president because his dad is dead, not alive, negating your main point.
Bishop73
His dad literally just died, and most people don't know the specifics of the naming rules. That would be a character mistake of the person introducing him.
When Tommy is made president and introduced, that's at the end of the film. So, no, his dad didn't literally just die. Plenty of time passed. But the correction is wrong on its premise, but that's not to say a different argument couldn't be made why the mistake is wrong.
Bishop73