The rats in the building change color from black to gray. In one shot they are clearly gray, but in the close-up, they are black.
Just before the rooftop fight sequence, the Shuriken in Alden's neck disappears and re-appears between cuts.
Master Shibata is supposed to be Japanese, but he speaks Mandarin with his students.
When the dead goon is thrown from the rooftop, it's clearly a dummy.
During the rooftop fight scene, the goon killed with samurai sword screams as he is thrown from the roof top.
At Master Ying's, when the sensei asks Charley Roman to perform a Kata, the microphone is visible during the entire scene, at the bottom of the screen.
The boom microphone appears throughout the movie.
At one point, Charley Roman introduces his sidekick, Speedy Little, to the duo's new member, Sup Kim. The dialog goes something like, "Speedy Little, Sup Kim. Sup Kim, Speedy Leacock." Leacock is the actor's last name.
One of the heroes tells Charlie to "take care of that chop suey chump" moments after the guy said he was Yakuza. Wrong nationality for the chosen ethnic slur, which the martial arts-trained speaker would have known.