When the general is changing rooms, he passes Tank's room, dressed in pajamas and robe. Moments later, when he's banging on the wall to Tank's room, he is in shirt and tie.
When Tony Curtis brings home bunches of roses to his wife and gets out of the car, they are all red. But when he is at the door of his house, there are yellow and pink flowers also.
Fourteen years pass between the 1952 and 1966 episodes, but none of the principals ages a single day, except George C. Scott grows a mustache.
While up North, Tom calls Tank. Tank has a cigarette in his right hand during the conversation, save for one of the cuts, where he has another phone in his right hand instead of the cigarette.
(at about 1h 12m) During the phone call between Tom and Tank, there are back-and-forth edits between the two, but in one of them Tank can be seen holding another receiver against his body, as if to mute the sound from the other call. There is no reason or explanation for this within the scene.
Tony Curtis is playing an attache, sometimes called a "dog-robber" in military slang. In a position like that he would be meticulous about his appearance. When the general arrives at the beginning of the film. The jacket Curtis's character is wearing is way too small in the sleeves. Something like that would never happen.
In the 1952 sequences all of Virna Lisi's hairstyles, makeup (including false eyelashes), and the cut and length of her uniforms are strictly 1966, not 1952.
At the end of the fight scene in the hotel room with the general next door, Julie Ferris says, "Boys! Boys! Boys!", but her lips do not move.
Near the beginning of the film at "an airport outside of London", there are substantial mountains visible in the distance.
When Tom is walking with General Parker after his arrival at the airport, Tom mentions the general has switched to "Churchill panatellas", meaning cigars. That is contradictory as both terms mean different sizes of cigars.
Tom refers to Tank as a "full bull" when noticing the full colonel insignia on his uniform. He should have said "full bird". Immediately afterwards, Virna Lisi gets her English mixed up and refers to the "maid days off" instead of the "maid's day off."