(at around 7 mins) When Merida hops on her horse and takes her "day off" she is wearing a royal blue dress. However, when she climbs the rock next to the falls, and on the top of the rock, her dress is dark green. When she goes back home, she is wearing a blue dress again.
(at around 26 mins) In the shooting competition, when Merida shoots her own arrow, the slow motion sequence shows that the arrow traces a small damage to her cheek. In the next scene in the castle the damage is gone again.
(at around 10 mins) Queen Elinor uses the term "collywobbles", meaning a stomach ache, a term not coined until 1823. Presumably we are hearing a "translation" of what the characters were really saying.
Merida's bow appears to be a double recurved self-wood type such as was used in the Great Plains area of North America during the 19th century. She also carries a quiver. Neither of these were used in any part of medieval Britain; bows were always self-wood (made of a single piece of timber) made without re-curves, while arrows for immediate use were carried tucked into the belt. At one point Merida carries an arrow in her mouth in order to follow up very quickly with a second shot - this was typical of native Americans of the Plains when hunting on horseback and in warfare. There are historic photographs by Edward Curtis of Plains warriors using this technique. It is definitely not recorded in medieval Scotland or elsewhere in Britain.
(at around 26 mins) The scene where Merida's dress splits, and reveals her corset, while amusing, is inaccurate given the movie's apparent medieval setting (around the 10th century). Corsets didn't come into fashion until Elizabethan times, approximately 600 years after the movie's apparent setting.
(at around 19 mins) One of the lord's sons says he battered many Romans on the beach. The Romans had ceased to be players in the British Isles, centuries before the time of the movie. Nevertheless, this boast was intended to make the Dingwall suitor appear more impressive to Merida and her parents, but resulting instead of being accused as a liar by a mysterious member of (presumably) the rival MacIntosh clan.
Angus seems to be a Shire or a Clydesdale, But neither of these breeds existed during the time period Brave was set in.
When the boys run the barrel through the blacksmith's tent, the smith hits his hand with his hammer, yet a ring of steel is heard instead of a squish of flesh.
(at around 8 mins) During the rock-climbing/waterfall sequence, the circling birds sound like red-tailed hawks which are native to North America.
(at around 6 mins) In the falconry scene, one of the birds is a Harris's Hawk which is native to the Americas.
(at around 35 mins) Even though the form of the spell that the Witch gives Merida is referred to as a "cake", it is not. It more so resembles a cherry mini-tart.