Show Tidbits
No laugh track is used during scenes that take place in the Operating Room.
For most seasons, the commercially available DVDs have an alternate audio track that omits the laugh track from the audio mix.
The characters who endured through the entire series (appeared in at least one episode of all 11 seasons) were Capt. Benjamin "Hawkeye" Pierce, Major Margaret "Hot Lips" Houlihan, Father Francis Mulcahy, and Corporal (later Sergeant) Maxwell Q. Klinger. Mulcahy and Klinger were eventually promoted to series regulars. Characters who appeared in 10 seasons were Nurse Kelley, Private Igor, and the psychiatrist, Dr. Sidney Freedman. Igor was played by two different actors. Jeff Maxwell played Igor in seasons 2 thru 11, with the exception of season 6, where Peter Reigert appeared twice as Igor. Nurse Kelley appeared in seasons 2 thru 11 as well. Sidney Freedman appeared in seasons 2 thru 11 also, but only appeared in one or two episodes per season, whereas Kelley and Igor appeared far more often.

Due to a legal technicality, the television show "Trapper John MD" is officially designated as a spin-off of the film version of M*A*S*H (1970). It would seem unlikely the show would have been produced had it not been for the popularity of the M*A*S*H television series.
Gary Burghoff (Corporal Radar O'Reilly) was born with a deformed left hand. The fingers on his left hand are shorter than normal. Such a condition would have likely disqualified him from military service. During the filming of the show, great care was taken to conceal the problem with his hand. Shot angles and blocking was arranged so that his left hand was not visible. Many times, his left hand was in his pocket. The principle means of obscuring his hand was through the use of props, such as a clipboard, file folder, or his teddy bear. Such attempts were not always totally successful. There are some instances where one can observe the condition of his hand by freeze-framing the video.
M*A*S*H was filmed on location at the Fox Ranch in Malibu or in a studio without a studio audience present. The producers had a disagreement with CBS regarding the use of a laugh track. The producers wanted no laugh track while the network did. A compromise was reached. The laugh track was not used for scenes that took place in the Operating Room. When a laugh track was used, it was more of a giggle and snicker track than loud guffaws and belly laughs. Some episodes omitted the laugh track entirely, such as "The Interview", the last episode of season 4.
Jamie Farr (Klinger) was promoted to a series regular in season 4. His name appears at the end of the opening credits.
William Christopher (Father Mulcahy) was promoted to series regular beginning in season 5. His name appeared at the end of the opening credits, after Jamie Farr (Klinger).
Many times, secondary characters, such as Nurse Kelley, Igor, and other nurses appeared on screen but had no spoken lines and were not credited as guest stars at the end of the episode. The nurses would appear in the OR or compound and Igor would appear in the background in the mess tent or the compound.
Starting as recurring roles, Father Mulcahy and Corporal Klinger were eventually elevated to main characters in later seasons. Of the 251 episodes, Father Mulcahy appeared in 206. Klinger appeared in 210.
Many of the guest stars who portrayed Koreans on the series were either of Japanese or Chinese ethnic heritage, rather than Korean.
After the first season, the secondary cast was re-tooled. Several characters who were carried over from the movie were dropped from the cast. Ho-Jon, Hawkeye and Trapper's house-boy, got a scholarship from Hawkeye's alma mater. Spearchucker Jones disappeared mid-season without explanation when the producers learned that no black surgeons served in a MASH unit during the Korean conflict. Ugly John, the anesthesiologist, was dropped without explanation after the first season. One new character was added during the first season, Corporal Maxwell Q. Klinger, who was perennially bucking for a section 8 discharge by crossdressing.
The voice heard over the camp loudspeakers was provided by actor Sal Viscuso.