Goofs

When Diabolik arrives at Valmont's plane it has a high wing with long legged main landing gear. Yet when the plane takes off it has a low wing and much different short main landing gear.

When Eva stops at the filling station, the road is only slightly wet. Two shots later, when she's being watched by the agent, it is raining distinctly and the road is really wet.

After the emerald heist, as Diabolik is pulling the "mirror" across the road, he is wearing no mask as he begins, then it cuts to a shot with his mask on, then he is mask-less once again as he finishes pulling.

When Valmont puts the emerald necklace in his jacket it goes in his right inside pocket, but when Diabolik removes it just afterward, he pulls it from the left inside pocket.

When Diabolik steals the lorry the driver runs after it. Diabolik then drives it quite a distance before he jumps off. After the lorry runs off the road the driver stops to look at the accident. Then Diabolik and Eva drive past the lorry driver without him having noticed that Diabolik had run back to the car.

Diabolik recovers emeralds from the ashes of a cremated body. Emerald, a type of green beryl, fractures and discolors when exposed to even mild flame (thus losing considerable value), and certainly cannot survive the intense heat of a crematorium.

Diabolik steals a 20-ton ingot of gold. The ingot is shown to be about the size of a VW minibus, but, because gold is so dense, a 20-ton block would take up much less space: a little over one cubic metre (36 cubic feet, or a cube-shaped block 39 inches each side).

Diabolik decides to hide the 11 emeralds by removing rounds from the magazine of his sub-machine gun; replacing each bullet by a gem, load them back into the magazine and fire them into Valmont. Since the emeralds are long and too wide the complete assembly would not fit back in the magazine. Even if it did the gem's cross section does not match that of the bullet so when the shell is fired most of the hot gasses would flow around it rather than pushing it out of the barrel. Finally, would the emeralds even have withstood the stress? It would have been far safer to just bury the emeralds, shoot Valmont, and retrieve the gems later.

Gold does not cool quickly enough in normal room temperature for a person to become a statue like Diabolik became.

In the Valmont crackdown newspaper montage, it is pretty obvious that most of the newspapers have been mocked up by sticking new headlines on; there are obvious edges and even wrinkles showing.

The picture that Diabolik mounts in front of the surveillance camera during the emerald heist would not be able to substitute the actual picture on the police monitor. Firstly it is taken with a hand-held camera without flash, and secondly after mounting it is only lit from the back and would therefore appear much darker on the monitor.

The gold ingot is lowered into its "coffin" using simple rope. Two strands of rope of this thickness would not be able to handle anywhere near 20 tons. (The lid of the "coffin" is however lowered using steel cables though.) Also gold is quite soft and flexible and should have more underneath support than what is given in the film.

When Ginko looks at the monitors one is showing the explosion outside the tunnel and the train slowly backing away from it. The other monitor is showing the train cruising backwards at considerably higher speed.

Obvious male diving stunt double for Eva.

In the first chase when the white Jaguar E-type is leaving the tunnel after the black Jaguar goes off a cliff, you can see the shadows of crew heads moving in the lower left of the frame.

What appears to be a light stand is reflected in the mirror-like surface of a cremation door.

The dummy Diabolik catapults off the roof is made in less amount of time than it would take anyone to just take his costume off.