Lewis Stone/Nayland Smith pokes around a Buddha. He sets down his gun, then falls through a trap door, with his gun clearly still on the Buddha. He gets up and pulls his gun out (of the same side of his coat, couldn't have two guns).
While he is Fu Manchu's prisoner, it is an important plot point that Sir Lionel Barton has had his hand cut off by Fu, his severed hand falling out of a tree and being discovered by Terrence Granville. But later, when Barton's body is abandoned in front of the expedition headquarters after his murder, he clearly (in long shot) has both hands.
Terry is severely whipped, but a short time later when he is strapped to Fu Manchu's table, all of the wounds have disappeared.
During his fight with two of Fu Manchu's minions, Terry's shirt is ripped to shreds. In the next scene when he and Nyland rescue their friend from the spikes, Terry's shirt is intact, although unbuttoned.
The mask that Fu Manchu wears near the end of the picture is not the same one retrieved from the tomb by the expedition. Fu Manchu's mask covers the entire face down to the top of his lips leaving the mouth and chin exposed, and is straight across along the bottom edge. The mask retrieved from the skeleton in the tomb has a diagonal slant on each side of the mask exposing a little more of the face.
When Fu Manchu mixes his mind control drug, a giant snake supposedly bites a "sacrificial victim," and Fu Manchu uses a syringe to extract venom from the victim's arm. However, the snake used in the scene is a Burmese python, which is non-poisonous.
As Fu Manchu is taunting Sir Lionel Barton with the consequences of the « Bell Torture » to which Barton is to be subjected, he explains that « the percussion and repercussion of sound against your eardrums will soften and destroy them until the sound is magnified a thousand times », thus depriving Barton of the ability to sleep. In fact, one of the principal consequences of a ruptured eardrum is hearing LOSS, not increased sensitivity to sounds.
Genghis Khan's skeleton is clearly a medical school skeleton. The removable top of the skull is very noticeable.
Obvious stand-in, special electrical effects wizard Ken Strickfaden for Boris Karloff where the electricity sparks off Fu Manchu's fingernails when he applies the electrical test to the fake sword.
Among the creepy creatures Fu Manchu uses to terrorize and torture his victims are American alligators and a Gila Monster. However, the film takes place in China, and these animals are found only in America.
Fu tortures Barton to obtain the whereabouts of Genghis Khan's mask and scimitar. Later on Fu is shown to have a serum that brainwashes people, so the torture of Barton was needless.
During the ringing bell torture sequence Fu Manchu's victim is slowly going crazy, but his two henchmen who have been ringing and listening to the same bell the entire time seem just fine. Standing to the right and left of the ringing bell as opposed to under may be not quite as loud but it surely it must have effected them as well.
On 3 occasions, Fu Manchu addresses Nayland Smith as "Sir Nayland" or "Sir Nayland Smith". Nayland Smith is a double-barrelled surname. His first name is Denis. Therefore he should be addressed as "Sir Denis". You cannot address an English knight as "Sir + his surname". Fu Manchu is highly intelligent and very well educated and would know this.