Ralph Bellamy (Randolph) and Don Ameche (Mortimer) make cameo appearances in Coming to America (1988) as the same characters; the two are now homeless, and Prince Akeem (Eddie Murphy) gives them a large amount of money to get them back off the streets.

Several funny moments in the film came about by accident. Mortimer Duke (Don Ameche) having trouble catching the money clip wasn't supposed to happen that way, but the actors kept going with it and not breaking character, so it was kept in the movie. Ophelia's "Swedish" disguise came about because Jamie Lee Curtis couldn't do the correct Austrian accent.

This was Ralph Bellamy's ninety-ninth film, and Don Ameche's forty-ninth. This was Eddie Murphy's second film, and he joked: "Between the three of us, we've made one hundred fifty movies!"

In 2010, as part of the Wall Street Transparency and Accountability Act, which was to regulate financial markets, a rule was included which barred anyone from using secret inside information to corner markets, similar to what the Duke brothers tried to do in the movie. Since the movie inspired this rule, it has since become known as the Eddie Murphy Rule.

(at around 1h 50 mins) Don Ameche's strong religious convictions made him uncomfortable with swearing. This proved to be a problem for the scene at the end of the movie, where he had to shout out "Fuck him!" to a group of Wall Street executives. When he did act out the scene, it had to be done in one take, because Ameche refused to do a second one.

George Folsey Jr.: (at around 5 mins) The executive producer appears as the first man to greet Winthorpe at Duke & Duke. (Dan Aykroyd refers to him by his real name with the line "Morning, Folsey".

Edie Falco: A young Edie Falco appears as a coach passenger, looking disgusted at Winthorpe as he bites into a salmon he lifted from the firm's party, at around the 81 minutes mark.

Continuity

The train leaving Washington, D.C. has a different style locomotive than the same train shown later in a pass-by shot.

(at around 12 mins) When Mortimer Duke is signing the paychecks, at least one of the shots is flipped horizontally. At first he signs with his left hand, then his right, then his left again. The part in his hair changes sides as well.

(at around 58 mins) When Ophelia first takes Louis to her apartment, it can be seen as she enters that she's wearing pantyhose. Later, when she removes her dress, she's wearing only panties.

(at around 1h 7 mins) When a man begins telling the "escargot" joke, Randolph and Mortimer are eating dessert. When the joke is over, the two are now eating dinner.

(at around 1h 50 mins) At the end of the futures trading sequence, Louis' and Billy Ray's trader ID badges, which have been a bright green, are the same gray as Billy Ray's suit.



Factual errors

FCOJ is subject to daily trading price movement limits. The 'swings' shown would trigger 'limit up' and 'limit down', and trading would be suspended for the day by NYMEX.

In the trading of the FCOJ, only the prices of the April contract change. In real life, the prices of all the future months would move.

Compartments on American passenger trains are always private. If Beeks had reserved one, no other passengers should have been allowed to enter.

Winthorpe's car, a Mercedes Benz 600 Grosser, is unique in that it features a complex hydraulic system that runs everything from the windows to the suspension. The car would need time to run and generate enough hydraulic pressure for the suspension to raise the car to proper operating height. It would not be possible for Coleman to just start the car and drive to work as is done in the beginning of the movie.

(at around 1h 16 mins) At the Christmas party when Winthorpe jumps on the table waving the gun, the clocks show that it is 1905 in Los Angeles, 2205 in Philadelphia and 0205 in London. London should read 0305. London is five hours, not four, ahead of Philadelphia, regardless whether in Daylight Savings Time (British Summer Time) or in Standard Time.



Incorrectly regarded as goofs

(at around 26 mins) When Billy Ray is released from jail, Randolph says that they are "the ones that bailed you out". Later, during the conversation in the limo, Billy Ray asks, "What about the police and the payroll?" The Dukes state that they have had the charges dropped. If the charges were dropped, then there would have been no need for bail. Bail is a conditional release/promise to appear in a future court date, which would not be necessary if there were no criminal charges.



Revealing mistakes

During early scenes in the movie, there's a fair amount of snow on the ground, but later scenes show a completely dry and snow-free Philadelphia. In fact, one overhead shot of Constitution Hall and the surrounding park shows green grass and leaves on the trees - highly unlikely in Philadelphia at Christmas-time.

The windows on the outside of Winthorpe/Valentine's house do not match the inside, and the foyer appears to be absent from the outside.

(at around 35 mins) In the large room when Louis is being framed, everyone is instructed to place the contents of the jacket pocket of the person to their right on the table. The people along the walls have no such tables as they are only sitting on chairs. The people on the right end have nobody emptying their left pockets.

The scene in the corridor of the train shows it to be a flimsy set as it shakes when people move quickly down it.

(at around 1h 45 mins) On the trading floor, the Secretary of Agriculture announces, "Ladies and Gentlemen, the Orange Crop Estimates for the next year...". The next frame shows Louis with his order pads facing the camera, completely covered in scribbles but no note taking or information on whom he bought from or sold to.



Miscellaneous

When Clarence Beeks is having his mouth taped shut, they are using black Gaffer's Tape, a low-tack-adhesive, non-spalling tape used by motion picture crews. Gaffer's Tape is not something that would be on a commuter train.



Audio/visual unsynchronized

(at around 1h 8 mins) When Louis is walking past the restaurant in the rain, the scene switches to him a number of times, and the rainfall can be heard. The first time, the camera shows a close-up of Louis; however, the camera is still inside the restaurant, yet the sound of rain falling drowns out the crowd noises in the restaurant that are heard continuously (other than when Valentine is making his prediction about the Russian wheat crop) when the camera is inside.

at around 1 hour 18 minutes when Valentine runs to the Santa walking in the road whom he believes to be Winthorpe he pulls down the man's beard and an Ow sound can be heard, but the man's lips do not move.



Errors in geography

(at around 34 mins) When the President of the Heritage Club announces that there is a thief among them, there is a Baltimore city flag standing right behind him.

(at around 54 mins) When Winthorpe is in the cab and Valentine is in the limo and they see each other, the street they are on outside Independence Hall has two-way traffic. This was only done for the movie. In real life, this is a one-way street heading east. The white lines on the street dividing the travel lanes can be seen, rather than a double yellow line which would be needed for it to be denoted as a two-way street.

(at around 28 mins) In the back of the Dukes' car are 2 clocks, showing times in Hong Kong and Kuwait. The difference shown is 6 hours; in fact, those cities are only 5 hours apart.

On the train from Washington to New York, the sound of the train passing railroad crossings is heard several times. Due to the electrification of the Amtrak Northeast Corridor line, nearly all grade crossings have been removed.



Plot holes

The Dukes ruin Winthorpe by framing him for robbery and possession of PCP. He's told he faces 3 to 5 years in prison. His girlfriend bails him out of jail, and later he meets his friends at a country club asking to borrow money for his defense fund to fight the charges. Yet after this, there is no further mention of his legal troubles, and the whole plot point is dropped. It's possible the Dukes made the whole thing go away (as they did with Valentine), but it's never mentioned.

At the Christmas party, Louis steals food, plants drugs, and threatens everyone, including a security guard, with a gun. Yet he is allowed to casually walk out of the building unimpeded with no one even bothering call the cops.



Character error

Near the beginning of the movie, the Dukes leave their mansion to a chorus of "Good morning Mr. Duke" from the various servants. A few moments later they are in the car and arguing about whether to sell pork bellies or to wait a few minutes to see if Winthorp's target price is reached. Mortimer says "the market's closing, we won't get the order in!" As it is morning in Philadelphia, the market would not be closing at this time.

(at around 28 mins) When Billy Ray is in the limo, Randolph Duke introduces himself and Billy Ray asks if the name Randolph is like Randy Jackson of the Jackson 5. Randy was not a member of the Jackson 5. He did not join the group until they became The Jacksons.

(at around 1h 28 mins) When Billy Ray enters the railway car that Beeks is in, it's hard to believe that Clarence wouldn't recognize him, as he's already encountered him twice before in the past few weeks.

After Louis Winthorp is released from prison, he tries to enter his house but finds the locks have been changed and the butler will not allow him to enter. The butler even threatens to call the police. In reality, the fact that this has been Winthorp's primary residence for years means that he can't be denied entry unless there is a restraining order or an eviction filed against him. And in that case, he would at least be allowed to collect his property from the building. Whether the Dukes actually own the building is irrelevant. Winthrop simply could wait for the police to show up and show them the address on his driver's license or demonstrate that he resides there any number of different ways. As an attorney, his character should have known this.

When the two hungry baggage handlers are leaving the gorilla wagon looking for food, after the bananas are snatched from them, the one leading the way pushes the door expecting it to open, but the motion quickly turns into a sideways push, as soon he realizes that's not how the door works. A baggage handler would be familiar with sliding doors and not make that mistake.