The number of soldiers under Li Shang's command continually decrease throughout the movie although no casualties are ever suffered.
Mulan's helmet flies off her head in the avalanche. But when she is left behind in the mountains, her helmet reappears next to her.
When Mulan, Ling, Chien-Po, and Yao dress up as concubines in order to defeat the guards to get to the emperor, Mulan is seen to have a green fan. But when she is on the roof with Shan-Yu, she pulls out a yellow fan.
When the remaining Huns emerge from the avalanche (observed by Mulan) and look down from the pass onto the Imperial City, the City is oriented with its front gate facing the pass. Moments later, when Mulan rides off to warn the troops, the Imperial City appears to have rotated, so that the palace is on the left and the front gate on the right.
When Mulan is chased in the camp and collides with the men standing in line to get their rice, rice flies out of the bowls of the men waiting in line.
The Huns could not have been the enemy of Mulan and her allies. The Huns were pretty much done by 469 CE and spent their time attacking the western and eastern empires of Rome, not the Chinese. The invasion of China that Mulan is alleged to have helped fight occurred in 600 CE. The Gokturks were the likely opponent that Mulan would have faced.
When Shang and his men are trying to break down the doors, they take the right statue which has its paw on a globe, meaning it is the male lion and is ruling the world. The statue to the left should have its paw on the belly of a lion cub, symbolizing a female lion with the children she will raise. However, the left hand statue also has its paw on a globe.
In the movie, the floor in front of the front door to the palace is the same height as the floor in the palace and there is no door sill. In real palaces in China, there is a small, six inch wide, foot tall sill on the floor between the outside courtyards and the rooms of the buildings to prevent invading enemies from running through the door. This worked because the leg pads and armor of the soldiers at the time were so heavy, it would take a lot of effort to lift their legs that high at a run.
The story is set in China, but the flag on the hospital tent where Mulan is recovering is the Japanese flag.
Cri-Kee has four legs, but all crickets have six legs.
Chien-Po is a normal human who demonstrates anti-law-of-physics super-strength by lifting seven soldiers from the cliff and also by holding Ling and Yao with one hand while searching for Mulan in the snow. This absurd personage is a classic stock character in ancient-war genre movies.
Shang leaves his sword in the mountains with his father's helmet on top of it, but when the Huns jump out of the paper dragon at the Imperial City, he pulls a sword out of its scabbard. However, it's possible he was borrowing the sword of another soldier or had acquired a new one while in the Imperial City.
When the matchmaker grabs Mulan's arm and the paint from Mulan's notes get on her hand, the paint is rubbed onto her face, but not on the handle of the teapot she gives Mulan.
During the "Honor to Us All" sequence, while the bather is bathing Mulan, the notes that Mulan wrote on her arm never smear away, even when we see her arms.
Shang shoots the arrow in the pole for the soldiers to retrieve, and although he shoots the arrow at a sharp angle, the arrow is wedged into the pole in a position that is horizontal to the ground.
After Mulan runs home from the matchmaker's place, she goes into her ancestors' shrine and wipes off her make-up, but no make-up is visible on her sleeves.
As the Huns crawl out from beneath the snow of the avalanche, there's not a trace of snow clinging to any of them.
When Mulan reads the Final Admonition and reads some of it off her arm, it was written in simplified Chinese. However, simplified Chinese was created in the 1950s. Mulan should have used the traditional Chinese symbols.
The primitive bamboo cannons (huochong) are known from AD 1132 onward, when General Han Shizhong used them in a city siege. The legend of Mulan is set around AD 600, and Huns are active a few more centuries before that. This weapon is way too advanced for era shown.
During the finale, Yao uses a banana as a part of his disguise. However, the banana is the sort of yellow and thin specimen a modern Western audience would recognize. This kind of banana cultivar would not be bred until centuries later. The bananas available in China in the era the movie is set in would have been rounder and of a different color.
When Mushu is chasing after Cri-Kee after Cri-Kee insults him, he says, "Whatcha mean, a loser? How 'bout if I pop one of your antennas off and throw it across the yard, then who's the loser? Me or you?" However, his gestures are exactly the opposite, first pointing to Cri-Kee, then to himself.
When Mulan says "Chien-Po, get the emperor" her mouth movements do not match with what she's saying.
When Mulan initially performs poorly at the training, Li Shang dismisses her and tells her to go home. However, she is reasonably young and fit, whereas her father can barely walk, so he certainly wouldn't have made it through the training and so there was no need for Mulan to be concerned enough to take his place.
All Chinese characters speak Modern English instead of (Old) Chinese.
When Grandmother Fa crosses the street in the middle of traffic but survives through it, Fa Li refers to her as "Grandma" when begging her not to do so. Grandmother Fa is actually the mother-in-law to Fa Li.