After General Kala announces the execution of Zarkov and Barin, there is a small scene when the gold faced guards are lined up and ordered to march by their superior (in some distorted voice). The distorted voice matches the mouth movements of the superior for several words, then doesn't as his mouth is closed. However, the voice continues to sound off.
At the very beginning of the film, Ming and his henchman are discussing "an obscure body in the SK system", which the inhabitants refer to as the planet "Earth", pronounced as if the word is completely foreign to them. However, at that moment, Ming activates a button on his console labeled "Earth Quake".
Again in the same fight, some of the spikes on the fighting platform can be seen folding under both Prince Barin and Flash's body as they fall on them (watch closely as the scene changes quickly), clearly showing that the spikes are made of rubber.
During the wedding sequence, Prince Barin is roaming around Ming's Palace. He is at one end of a corridor when he shoots one of three guards who appear from around a corner at the opposite end. When we next see him, Prince Barin and the remaining two guards have switched positions (Prince Barin is now standing over the body of the guard whom he initially shot down).
There are many blue-screen compositions where characters or items appear partly transparent. This is probably due to the copying process for the travelling mattes that were used to superimpose the effects shots over one another.
When Flash and company first arrive at Ming's palace and see the floating orb droid for the first time, three wires holding it are clearly visible. Later as it floats down the hallway two holes punched in the extended pieces are seen where the wires are threaded through.
In the shot of Vultan speaking to Flash after Ming dies, there is a Gold Helmeted Guard laying (apparently) dead in the rubble near Vultan's feet. The actor playing the guard moves his head slightly forward then stops.
When Princess Aura is showing Flash how to fly the ship when they are traveling to Arboria, she tells him, "The left lever controls direction, and the right controls altitude". Moments later while still flying, Aura tells Flash to take a left over Frigia. She pushes on the right control lever.