(at around 29 minutes) The protagonist claims that a lack of sunlight has left him deficient in vitamins A and E. Vitamins A and E are obtained from the diet; sunlight only contributes to the synthesising of vitamin D. Consequently, he should only be deficient in vitamin D.
(around the 18-minute mark) Shortly before the scene in which Dae-su Oh encounters the man about to jump from the roof, there's a brief beat where he notices the man is wearing an expensive suit and a watch. However, when he grabs him the watch is already gone.
(at approximately 1h 45 mins) Woo-jin cocks his gun twice in quick succession: once just before he's about to shoot himself in the head alongside Oh Dae-su, and once in the flashback while he's in the lift.
(at around 28 minutes) As Oh Dae-su loses consciousness after eating the octopus, filming equipment can be seen reflected on the silver serving platter as the shot pulls back.
(at around 1h 50 mins) When the lift doors open to reveal Woo-Jin's suicide, a man in a white shirt, possibly a crew member, can be seen in the reflection to the right.
Around the 35-minute mark there appears to be a mistranslation of one Chinese character. Dae-su and Mi-do visit several restaurants labelled "Blue Dragon" to sample the dumplings, but the Chinese characters actually translate as "Green Dragon".
(at around the 34-minute mark) The common surname "Ljungberg" would not be used in conjunction with the honourific "Von", and "Von" is very uncommon in Sweden.
(at approximately 34 minutes) The address for "Eva Von Ljungberg" is incorrect both in format and in fact. Although the street address itself is correct, it refers to a hotel rather than a residential building. A PO Box is almost never used together with a street address. The postcode is also wrong: it should begin with 12, not 10; postcodes beginning with 10 are allocated to large organisations and are not linked to a physical street address as shown on the note.
Although he is held captive and cut off from the outside world for 15 years, Oh Dae‑Su is portrayed as knowing how to operate a contemporary mobile phone — a device that would have been exceedingly uncommon (and markedly different from the clamshell handset he owns) in South Korea when he was imprisoned in the late 1980s. Nevertheless, Dae‑Su watched television throughout those 15 years, so it is highly likely he would have seen a modern mobile phone in use at some point.
(around the 40-minute mark) When Dae-su enters the room of one of his nemeses, his monitor displays stock market information. The internet address shown is: C:/DocumentsandSettings/[...]/#OldBoy#/[...], which therefore points to a folder on the computer rather than an internet address.
At approximately 1 hour 50 minutes, whilst Woo-jin Lee was pulling Lee Soo-ah's hand on the bridge, one shot briefly revealed a dummy used as Yoon Jin-seo's stunt double.
