The opening and ending scenes have Colonel Potter leading the 4077th in celebrating the end of the year 1950 and 1951 respectfully. In his initial appearance in Season 4's "Change of Command", Potter replaces Colonel Henry Blake as Commanding Officer, and it is announced that the date of his arrival was September 19, 1952. Therefore Colonel Potter would not have been at the 4077th on New Year's Eve 1950 nor 1951. Neither Maj. Winchester nor BJ Hunnicut should have been there either, given the time they arrived in relation to Col. Potter. This also means Radar, Captain McIntyre, and Maj. Burns should have been present as well.
When the Giants win the pennant, Winchester drops his baseball cap to the ground. Moments later, he has fainted and is lying on his back, but the cap is back in his hand and being held to his chest.
While Potter might not have given Klinger his Section 8 discharge because Potter knows Klinger is only pretending to be insane, after Klinger's nth discipline for not wearing authorized uniform, the brass would have no choice but to discharge him for willful disobedience (failure to wear correct uniform while on duty).
When Winchester faints after hearing the baseball scores, he's shown lying on his back. A person that faints falls forward, a fact Winchester pointed out to Klinger at one time.
Although The 4th of July would be a good reason to have a picnic and celebration it's unlikely they would have allowed fireworks to be shot up to explode in the air due to the fact they were in a war zone.
When Klinger is pitching softball to Col. Potter, he is clearly wearing a 1970s-era baseball glove, not the kind available in 1951.
The broadcast of the 1951 pennant game that the 4077th listens to is a recording of Russ Hodges' famous live description. However, that broadcast was heard live only by local Giants fans. Most listeners would have heard Gordon McLendon's description.
When Hawkeye and BJ determine the artificial kidney machine they made works, Hawkeye tells the patient they're using it on that he'll be able to be transferred to another hospital where they don't have a kidney machine that looks like it was put together by Mr. Wizard. "Watch Mr. Wizard" began airing in March 1951. As this episode starts out New Year's Eve 1950 to ring in 1951, it is unlikely either Hawkeye or BJ would have seen Mr. Wizard.
When Father Mulcahy enters Klinger's 'office' while Margaret, BJ and Hawkeye are arguing, a wall of the studio with plywood attached can be seen in the background, not the canvas 'wall' of the Swamp with the sky above.
In early 1951, Father Mulcahy plants a corn field. This corn field is shown to be present throughout the year/episode. This is a MASH unit. As both Potter and Hawkeye notes in Cementing Relationships (1980), the "M" stands for mobile. On occasion, they have to move the hospital. Yet, the constant presence of the corn field would suggest that they did not move once, throughout all of 1951.
Klinger refers to Colonel Potter as the "top kick." Top kick is an informal term for a first sergeant.
Igor is derided for creaming the corn that Father Mulcahy grew, and his response indicates he did do this. However, as established elsewhere in the series, such as in "Morale Victory," Igor is not the cook; he merely serves the food that the cook makes.
The two Colonels discuss their cavalry units' actions during WW1 in France.
No US cavalry unit was in action in WW1.
No US cavalry unit was in action in WW1.
When a ball knocks over her tote bag, containing yarn, Margaret complains to Klinger, "you're unraveling my potholder!" As long as the stitches are all on the needles, the potholder can't unravel. Her yarn, however, unrolled on the ground and got muddy.