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.
The film was conceived as a vehicle for Gene Wilder and Richard Pryor. But when Pryor dropped out and Eddie Murphy came on board, he made a motion to get Wilder replaced because he didn't want people to think he was just trying to be another Pryor.
Eddie Murphy later admitted that while on the floor of the stock exchange in the final scene, he only followed the script, he had no idea what was going on as he found stock trading incredibly confusing.
The story about the Dukes' cornering of the orange juice market was probably inspired by the "Silver Thursday" market crash of 27 March 1980, during which the Hunt brothers of Texas tried to corner the silver market and subsequently failed to meet a $100 million margin call.
Several funny moments in the film came about by accident. The scene where Mortimer is trying to catch the money clip and having trouble wasn't supposed to happen that way, but both kept going with it and not breaking character, so it was kept in. Ophelia's "Swedish" disguise came about because Jamie Lee Curtis couldn't do the correct Austrian accent.
When Winthorpe and Valentine arrive at the World Trade Center, Winthorpe tells Valentine "In this building, it's either kill or be killed". This line was removed from some TV broadcasts after 2001, out of respect for the victims of the September 11th attacks.
The exterior shots of Louis Winthorpe's house are of a real house on a very affluent street in Philadelphia. The wreath on the door was replaced when the producers wanted something bigger and better. They borrowed a hand-made wreath from a house across the street.
The theme of rich men taking in a bum and passing him off as an aristocrat is reminiscent of the George Bernard Shaw play Pygmalion, and also includes specific elements of Hoi Polloi (1935), a previous American film parody of the same play. The theme of a rich and poor person exchanging positions in life comes from the Mark Twain novel The Prince and the Pauper.
A scene in the movie not included in the final cut but seen frequently when the movie is shown on television (presumably to fill a longer time slot with commercials) occurs after Clarence Beeks talks to the Dukes via telephone and Billy Ray eavesdrops on their scheme. In the original cut, Beeks goes from the phone booth to the Amtrak train platform, holding the briefcase with the crop report. In the added scene, we see Beeks procure the reports from a secured vault where he pays off a security guard and opens a safe-deposit box.
In the opening montage of Philadelphia there is a shot of the Rocky statue erected in Rocky III (1982) that was released the previous year and was still sitting at the top of the "Rocky" steps in front of the Philadelphia Museum of Art. The statue now resides at the base of the museum steps.
Winthorpe's watch - a "Rouchefoucauld" is named after French writer François de La Rochefoucauld. Winthorpe names six cities with the intention that the watch tells six different time zones, which is not the case. Monte Carlo, Paris, Rome and Gstaad all share the same time zone, so the watch tells only three.
The home used in the film is not the Rosenbach Museum and Library, but is a private home two doors west. Both houses, however, were built at the same time and originally had an identical floor plan. During the filming of the movie, DeLancey Place was closed for a few days. Denholm Elliott was the only actor in the film to visit the Rosenbach. The staff of the museum were all given Pennsylvania State Film Commission tee shirts.
The barbershop quartet song sung by Todd and his pals at the tennis club is sung to the tune of "Aura Lea" an American Civil War song written by W.W. Fosdick (words) and George R. Poulton (music). Elvis Presley's "Love Me Tender" is a derivative of it as well. Another version of Aura Lee is done in Revenge of the Nerds (1984). It's the song the Pi's sing to offer themselves as dates to the the Tri-Lambs (Hello Lambdas we're the Pi's/And we're here to say/We think you are special guys/Lambdas all the way...)
Randolph Duke has a picture of Ronald Reagan on his side of the Dukes' shared desk, while Mortimer has a picture of Richard Nixon. Bryan Clark who portrayed Stock Exchange Official #2 has often played former President Ronald Reagan.
Frank Oz has a cameo as a police officer who is checking in Winthorpe's property when he gets arrested. In The Blues Brothers (1980), he plays an officer who is giving Jake Blues his property back to him.
The trivia items below may give away important plot points.
Randolph and Mortimer Duke later appear in Eddie Murphy's movie Coming to America (1988), where, in a cameo appearance, the two are homeless on the street and Prince Akeem gives them a large amount of money to get them back off the streets.
Don Ameche's strong religious convictions made him uncomfortable with swearing. This proved 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.
The main titles are accompanied by the overture to "The Marriage of Figaro" by Wolfgang Amadeus Mozart, and in an early scene, as Louis is leaving his office he whistles the beginning of the aria "Se vuol ballare" from the opera. In that aria, Figaro declares his plan to turn the tables on his master - just as Louis and Billy Ray will eventually outwit the Duke brothers.