Throughout the series, Douglas MacArthur is referred to as though he is still in command of the UN forces in Korea. However, MacArthur was relieved of command by President Truman about ten months into the war.
During one scene in Col. Potter's office, Col. Potter is spelling someone's name on the telephone. Hawkeye, standing nearby, responds by chanting "M-O-U-S-E" - part of the "Mickey Mouse Club" show's theme song. The "Mickey Mouse Club" did not debut on television until October 3, 1955, more than two years after the ceasefire that ended the fighting in Korea.
Few of the primary characters past the first season wore the correct haircuts/hairdos for being members of the US Army in the 1950s. As the series continued, only Colonel Potter ( Harry Morgan) looked as if he could have been a military officer or member in a 1950s Army unit.
The social attitudes about race, sexism, homosexuality and class that were expressed by characters in the series were those of post Civil Rights/post- Vietnam eras when the series was filmed, not those of the early 1950s when it was set. As the series continued, it began to resemble a modern drama rather than a historical re-telling of earlier events.
In a number of episodes the team is in a tent watching movies. The movies are usually run on a Singer 16mm projector which wasn't manufactured until years later. In reality, the unit would have been issued a Bell & Howell JAN (Joint Army/Navy) projector with a three clawed mechanism that was highly regarded for its durability and ability to project less than perfect prints.
Throughout the series, Margaret has very long fingernails. As both a nurse and a Regular US Army officer who's a sticker for the rules, there's no way her nails would be so UN-regulation. Neither nurses nor Army officers have long fingernails.
There are various episodes with Korean nationals such as farmers, villagers. These Koreans speak English. It is highly unlikely that the native Koreans would speak or understand any English especially in small villages away from a city.
BJ's daughter Erin's age is constantly jumping back and forth. When he first arrives, he explains that he received his orders to report after returning home with his wife from their first night out after Erin was born. When Radar leaves, Erin is big enough to walk up to Radar and call him "Daddy." In the next season, BJ explains that on his last anniversary, Peg was still 8 months pregnant with Erin, which would make her less than 1 year old. A few episodes later, Erin is once again talking in full sentences and is nearly 2 years old.
In Harry Morgan's first season as Colonel Potter his only child is a son whose wife has a daughter. Later on he has a grandson named Cory who went from a newborn to being a five year old. However, by the end of the series his only child has become a daughter and her husband visits Col Potter at the 4077.
Hawkeye's background and family situation changes quite a bit during the run of the series. At the beginning he is from Vermont, both parents are living, he has a married sister that sends him an oversized homemade sweater, and a nephew. By the end of the show, he is from Crabapple Cove, Maine, and he is an only child whose mother died when he was about 10.
Several of the characters had multiple variations on their names during the series, perhaps none more so than Father Mulcahy. His name is given at various points as John, John P., Francis, Francis John Patrick, and John Patrick Francis
Although the Korean war lasted slightly over than three years (Summer of 1950 through Summer of 1953), MASH seemed to pack at least four or five Christmases throughout its run. Of specific note: Dear Dad - 1972, Dear Sis - 1978, Death Takes a Holiday - 1980, Twas the Day After Christmas - 1981.
Throughout the entire series, the nurses referred to as "Baker" have been different women, including one (in contrast) black woman, some (in contrast) single women, and a married one, whose husband Tony spends the night with her in Hotlips' tent.
In the early seasons, Vietnam-like references were often made by characters: Claiming their location was in "Southeast Asia" (Korea is in northeastern Asia) and searching for missing colleagues in "the jungle" (there are no jungle regions in Korea).
Franks Burns and Hot Lips Houlihan's affair would have been far more scandalous in the 1950s setting of the series than in the 1970s/1980s airing. Since Burns was a married man, violations of military law would have been an issue and the affair would have quickly ended or resulted in both being removed from the service.
Very few of the actors are the right age for their characters. Hawkeye, Trapper and BJ are supposed to be just out of residency, yet all were portrayed by actors in their mid-30s or older. Max Klinger was portrayed by Jaime Farr, in his late 30s, but a draftee would've been 18-21 or so.
As a rule in the service, a person is only awarded one Purple Heart (the first time they're wounded) and then oak leaf clusters for subsequent injuries. However, multiple characters throughout the series have or receive more than one purple heart.
Characters are often shown very close to the blast of artillery shells. The blast is not the danger, but the flying shrapnel from the shell would have been and as close as they were the would have been hit.
The "Section 8" discharged (also known as a "blue slip" (as it was printed on blue paper) was discontinued in 1947, before the Korean War. It was replaced by General, Medical or Dishonorable discharge, depending on the case.
In several episodes, Radar misinforms another character about the time difference between Korea and the United States. During one attempt to call a stock broker in New York City, Radar tells Maj. Burns there is an 18-hour time difference. The time difference between Korea and New York is 14 hours during standard time months and 13 hours during US daylight savings time.
Klinger is a fan of the Toledo Mud Hens minor league baseball team. The Mud Hens are an affiliate of the Detroit Tigers. Yet he wears a cap of the major-league Texas Rangers, who didn't start play until 1972.
Three different people have been named "Nurse Baker", including a single woman, a married woman and a woman of a different race (she was Black while the other two were Caucasian). However, Baker is a popular American name, and could have been shared by more than one person in the 501st. In addition, "Baker" is the second entry in the old US Navy radio alphabet. "Able," the first entry, is the name of several nurses throughout the series. "Able" and "Baker" appear to be placeholder-type names, possibly an in-joke for military viewers.
Two sets of the camp were built, one in the outdoors, and one within a studio. This is apparent in numerous episodes when the characters are standing "outside" in broad daylight, but each cast member has numerous shadows as a result of studio lights shining in different directions, as well as an echo within the studio that is not audible on the outdoor set.