Continuity mistake: When Ming is about to die, he slips away from the spike, which has parts of it covered in green blood. When Flash sees him, the spike is fully covered in green blood.
Continuity mistake: The pilot hands Flash a People magazine to sign. When Flash sits down to autograph it, one can see it's already signed (seemingly from previous takes). Then he scribbles on the same spot again.
Continuity mistake: When the movie begins, Flash is reading a newspaper, sitting sideways, his back leaning on the door. When Dale's van arrives, he is facing straight, with the paper resting on the steering wheel. Then the shot changes to the first position and he turns sideways towards the wheel.
Continuity mistake: During the plane flight, the sky outside keeps switching back and forth between cloudy or puffy clouds opening to let a red light, depending on the angle.
Continuity mistake: The hot hail that falls on the hood of Flash's car disappears in the later shots.
Continuity mistake: When the plane enters the greenhouse the cabin is empty. Then in the close-up Flash and Dale have appeared inside.
Continuity mistake: When Ming walks in the room where Dale sleeps, her thigh swaps from covered to uncovered and the cushion moves around depending on the angle.
Continuity mistake: After the meteorite on Munson's bed starts burning, his hand moves from down to up and is now holding a pen and paper, despite him being asleep. Also the cup on the table moves around between shots.
Continuity mistake: When Flash greets the martians he's handed a gun which makes him crouch and twist to the left. When the angle changes he is now standing tall and his hand is at chest level instead of waist level.
Continuity mistake: When Ming orders to send another charge against Sky City the sky swaps from sunny in the wide angles, to cloudy in the close-ups in barely half a second.
Continuity mistake: When the laser scans Zarkov's jacket to destroy the gun inside, the arm disappears in the close-up angle.
Continuity mistake: The FX of the rainbow coloured dangerous void is missing before the fight starts, revealing a grey coloured, harmless set. (01:09:45)
Continuity mistake: When lizard man is fried, the position of his tail keeps changing between angles.
Continuity mistake: After Barin stands up on the spiked ring his whip keeps changing positions depending on the angle.
Continuity mistake: While fighting against Barin, Flash's whip lies on the floor and keeps changing from rolled to straight between shots.
Continuity mistake: When Zarkov is waving a piece of cloth to signal Ming their position, Flash and Barin are standing behind, but disappear when Ming watches Zarkov on his screen, and reappear afterwards.
Continuity mistake: After Barin saves Flash from the Arborian beast Flash's shirt is clean, a frame later from a different angle it's covered in mud.
Continuity mistake: When Aura is kissing Flash and telling him about her palace, she has her arms around his ears. When the angle changes the hands are around his cheeks.
Continuity mistake: Zarkov tells Dale to press the button to launch the shuttle, and Flash leaves the place with a big cloud of smoke behind. Half a second later, from a different angle, the smoke is gone.
Continuity mistake: When Flash's plane lands in Zarkov's lab the amount of leaves on the windshield increase dramatically between one frame and the other.
Answer: Spider.