In many of the fight scenes, especially those involving the Landlady, the combatants are often talking and fighting at the same time, but in the wide shots of these scenes their mouths aren't moving.
Just before the final fight, where Sing is standing on the platform on the stairs, when the camera rotates around Sing in a 360 degree circle, you can spot a crew member's head in the corner of the platform.
The leader of the Crocodile Gang's hat changes as he leaves the police station, going from a straw cowboy hat to a shapeless fabric hat and back to a cowboy hat by the time he gets downstairs.
When Tailor's rings are broken he falls backwards and the pieces fall to the ground all around him. In the next shot when he is getting up no pieces can be seen on the ground.
When Rabbit-tooth Jane sits down in front of her mirror to do her make-up, she's already wearing lipstick.
When the Beast and Sing are fighting, one of the Axe Gang can be seen crawling near a rusty barrel in the background. In the next shot the gang member vanishes as they pass the same barrel.
After Brother Sum has covered the mother and child in fuel the mother's hair drapes down her face and covers her forehead. In the following shot when Coolie catches the lighter, her hair is combed back out of her face.
When Sing is running away from the landlady, when Sing is about to hit a truck, he moves to the left and another truck is there, after he runs underneath the truck and the landlady jumps over it, the other truck disappears.
When Coolie takes on the Axe Gang alone, before the tailor joins in on the fight, an Axe Gang member is seen taking a perfect unblocked swing at Coolie's back and then realizes that Coolie couldn't block it so he runs away.
After Sing breaks the table leg over Beast's head Sing is seen tossing the leg on the floor as Beast approaches him, yet the rest of the table leg makes no sound as it hits the ground.
When the Beast and Sing first start to fight, Sing punches the Beast. The Beast goes through the railing facing away from Sing. In the very next scene when Sing kicks the Beast, he is facing Sing.
When Sing is fighting the gang at the end, before he begins to fight the Beast, he stands on a balcony and throws two bad guys away from him, and you can see them landing against the wall of the balcony, but in the next shot you see them crashing right through the wall and out of the balcony.
After the final fight, when Beast is looking up to Sing, he's also facing the sun. In the next shot, the sun is on Beast's right.
When the Landlord comes into Tailor's shop at the beginning of the movie, Jane is seen holding some type of pink material, and yet in the next shot when she is running the pink material she was holding has vanished.
When Brother Sum is about set the children alight, he throws the lighter and it falls just a foot away from his feet, but then we see it flying dramatically through the air above the children's heads.
At one point when Donut is fighting the Harpists, he is holding two spears in his hand. When these are broken, Donut drops them and jumps up. The spears disappear into thin air after he drops them.
In the first big fight with Axe's gang, when the luggage carrier of the car opens, the camera is reflected in it.
In the fight scene with the two blind players, when the tailor throws the concrete wheel at them, the player flips the instrument so that the strings are facing down. When the camera angle changes, the strings magically appear up.
After the final fight, the camera looks at Beast from the front during a conversation and you can see his hair. The camera switches to the rear before he is punched and the hair is gone; it is clearly a stuntman.