Factual error: The hat that Brad Pitt wears in the 1985 scenes is a Padres hat with navy, orange and white as the colours. In 1985, the Padres' colors were brown and yellow. The color change didn't come until late 80's or early 90's.
Factual error: The "American Consulate in Hong Kong" is actually the HSBC building. The actual consulate building is nearby, but perhaps not so photogenic.
Factual error: In Suzhou Prison, presumably the Suzhou near Shanghai, all the prison guards are speaking Cantonese, which is a southern dialect. They should be speaking either Mandarin (Putonghua) or their regional dialect.
Factual error: In the scene where Brad Pitt meets Robert Redford on the roof of a house in Berlin in (I think it was) 1980, you can see a lot of GSM transmitters. GSM cell transmitters didn't come until 1993.
Factual error: At the end of the movie it is about 7:42am in Langley, Virginia. In Suzhou, Tom Bishop is being rescued out of the prison and as he is being flown away you see sunlight poking down through the clouds in the backdrop. It would be 8:42pm there. Since they showed the Berlin wall falling on the news that would put the film at the beginning of November in 1989 where it would be dark at 9pm.
Other mistake: During the scenes in Beirut, we see a picture of a militiaman firing an RPG at an armored vehicle. If you look at the launcher, you can see that there is no grenade in the launcher when it is "fired."
Factual error: Satellite photos on Robert Redford's desk depict Suzhou as lying on the coast of China. In fact it is far inland.
Continuity mistake: When Nathan and Bishop are on the rooftop talking, Bishop is seen pulling a chair over so he can sit down. The camera angle changes and he's seen pulling the chair over again.
Factual error: In the scene where you can see Robert Redford sending a fax, there is a Tux doll (Linux mascot) on the wall. Funny, but this scene happens in 1991 and Tux was first designed in 1996. (01:40:24)
Factual error: There would never be a US Embassy in Hong Kong - only a consulate.
Continuity mistake: When Nathan starts making his lunch plate from the food that is in the room, he is seen grabbing a spoon but after the camera angle changes to a front view the spoon is not in his hand nor on his plate.
Factual error: Redford's character speeds towards his office in Langley, Virginia driving his Porsche. As he passes a Georgian style building and the camera position, road markings (zig zag lines, metal road studs and a 'keep left' bollard) are all momentarily visible. This very short scene was obviously filmed on a UK road, certainly not in the US. (00:08:30)
Continuity mistake: Right after Bishop makes it to the balcony, the scene changes to them in a bar drinking and you see Nathan taking a drink and then putting his glass on the bar. The camera angle changes to a close up and the glass is now near his mouth.
Factual error: Bishop is drinking out of a cafe in Beirut, just in front of Elizabeth's hotel. There is a Coca Cola logo on the tend, but this logo will appear only in the '90s.
Factual error: Part of the movie is set in Beirut during 1985. Periodically, there are scenes with Robert Redford's character working from a command post in the American Embassy. Behind him, is a quite modern looking 15" monitor. The interesting part is that although the monitor looks out of place, the makers of the movie saw fit to fill the screen with monochromatic "green" information, which would be consistent with 1985.
Continuity mistake: During Bishop's first mission for Nathan, he kills a general in Vietnam. The first shot hits the general in his chest on his right side. The second shot hits the general in the head, but the bullet hole from the first shot is now gone.
Continuity mistake: As Bishop is pulling the doctor through the mob of people you can see someone has the back of Bishop's shirt and is trying to hold on to him. The camera angle changes to a front view and no-one is holding onto the back of his shirt anymore.
Continuity mistake: When Nathan is training Tom, they are in a park and Nathan tells him to extract info from someone. Tom unfolds his arms and starts walking towards a woman. The camera angle changes and he is seen unfolding his arms again.
Continuity mistake: When Bishop gets the the medication past the checkpoint for Elizabeth, she is seen greeting a man with a handshake and when Bishop goes to take a picture of them, she is seen greeting him again with the handshake through the camera lens.
Factual error: Robert Redford's call to the London Stock Exchange to liquidate and transfer his holdings to the Caymen Islands makes no sense. The LSE does not provide that kind of service, it is a regulatory body which admits companies to the Exchange and regulates them. In reality he would have called a bank or stockbroker to execute this type of transaction. And that banker or broker would not have been sitting in the LSE building on Old Broad Street in the City of London. There is no physical trading floor at the LSE, in the way which is depicted in the film, for the banker or broker to work from.
Chosen answer: He might have taken a medical equivalent to a regulated dose of Curare, which can suspend the body temporarily in a coma-like state, while keeping the mind active and perceptive. It could also have been tetrodotoxin, which has remarkably similar effects, but lasts longer. In either case, they were specifically engineered for his physiology, indicating a pharmacologist's aid in their endeavor.