Other mistake: Two cars with the same license plate numbers are seen as the minions are hitch hiking on the road. The plates of the hippie wagon and the old lady's car both read D-6413.
Factual error: When the minions are attempting to purchase tickets to get in to see/steal the crown, the admission prices on the wall are priced as £s and pence (decimal currency). As this was 1968, Britain was still using pre-decimal pounds, shillings and pence.
Other mistake: In the end credits, the additional voices are listed alphabetically by last name (column form); however Carlos Alazraqui is listed before Lori Alan.
Continuity mistake: Kevin's, Stuart's, and Bob's goggles change from brass to steel between when we last see the goggles in the rowboat to when they climb ashore in New York. (00:11:40)
Factual error: American style fire hydrants are seen at least twice, but they aren't used in the UK.
Continuity mistake: Bob's right eye keeps changing color back and forth between green and brown.
Continuity mistake: Before the minions gets to Scarlet's coronation it's daylight, but when they escape from the villains it is completely dark.
Factual error: During the night chase scene through London streets, a subterranean vehicle emerges from the ground. The drill head is turning in the wrong direction and would be ineffective for the same reasons as turning a screw in the wrong direction.
Factual error: While hiding in the arctic cave, one of the minions eats a banana. However, the minions are supposed to have been trapped there for many years and edible bananas are restricted to tropical or near-tropical regions, roughly the area between latitudes 30°N and 30°S. It would not be possible for them to have bananas.
Continuity mistake: Before the dinosaur falls into the lava pit, a minion rolls under a rock. He lands face up, but a shot later he is facing sideways. (00:03:10)
Factual error: When Kevin, Stuart and Bob are honored at the end of the movie in front of Buckingham Palace, the Union Jack can be seen flying on top of it. The only flag displayed on Buckingham Palace at that time was the Royal Standard, and only when the regent was in residence.
Suggested correction: One of Bob's eyes is green and one brown so when he faces left or right one side is green and one is right.