Pernell Roberts publicly denounced series television when he left Bonanza (1959) for theatre in 1965. He decided to return to television because his salary would help support his aging father. He also felt that he would be able to exercise his acting range and address social issues, two things he felt he was rarely able to do on "Bonanza".

Wayne Rogers, who played Trapper John in M*A*S*H (1972), turned down the role because he did not want to play a doctor again on television. (He later played a doctor on the television show House Calls (1979), itself a spinoff of a movie, House Calls (1978).)

When Mary McCarty died during the hiatus between the first and second seasons, her absence was explained by having her character get married and move away.

During the course of the show, Trapper drove three different cars: a 1978 Mazda RX-7, a 1980 Dodge Mirada CMX-360, and a 1983 Cadillac SeVille.

The name of Gonzo's (Gregory Harrison's) RV, was the "Titanic"

In the book, "MASH: A Novel About Three Army Doctors," by Richard Lee Hooker, Trapper's nickname, we are told in the book by the author, came to him because he was caught having sex with a woman on a train. When the woman was confronted about the incident, she said, "He trapped me!" Hence Trapper. Calling him Trapper is essentially like calling him "Rapist!"

At one time, 3 different TV shows were linked together; 1. M*A*S*H, which originally had a character named Trapper John, played by Wayne Rogers, 2. Trapper John, M.D., which took this character into civilian life long after the war, and 3. House Calls which starred Wayne Rogers, who had previously played Trapper John on M*A*S*H.

We learn in the book and movie and television show MASH; that Trapper John's full name is John Francis Xavier "Trapper" McIntyre. They never mention that on the show though.

Richard Hornberger was a gifted surgeon whose memoire of his experiences, "MASH: A Novel of Three Army Doctors", became the basis for the hit 1970 Robert Altman film; as well as the hit 1970s television series bearing the same name. Trapper John MD was one of the lead characters in the movie and TV show. We have since learned from numerous articles that have come out, and the 2010 documentary "The Real MASH"; that Trapper, Hawkeye, Margaret and others were based on real people. Trapper John Macentire, Hawkeye's wingman, was based on another doctor that served in the 8055th with Hoernberger and befriended him. Dr. James Dickson was a young doctor from Ohio who was friends with Hoernberger and was the prototype for Trapper John MD.

1990s-era Murfreesboro, Tennessee rock band, "The Brancuzzis", was named after the character of Nurse Brancusi.

In the 1984 to 1985 season, there were three spin-offs of this show being broadcast on network television simultaneously: AfterMASH (1983), W*A*L*T*E*R (1984), and Trapper John, M.D. (1979).

A court ruled that the series was not a spin-off from the television show M*A*S*H (1972). Rather, that it was a spin-off from the film MASH (1970), and yet, in the pilot episode, you can see, as they pan through Trapper's office, the photos on the wall, the one of Alan Alda and Wayne Rogers, who were in the television series, and not Donald Sutherland and Elliott Gould, who were in the movie.