When Inspector Gadget is having fries at the science fair, the fries box is full, then half-empty and then full again.
When Claw's get away van runs over the bubble gum, in the following shot there is no trace of bubble gum stuck to the van's wheels.
When you see the truck at the warehouse, there is no wall between the front and back and the truck is loaded full of standard gold bars in stacks, and several sacks of coins. However, when you see the overhead view of the truck as the rocket ship emerges, there is a wall between the front and back, there are no sacks, the gold bars are much smaller, and the stacks of bars occupy much less of the space than before.
The amount of bubble gum goo on the Chief's hands, after accidentally setting his hand in it.
Gadget's fake mustache changes position in between shots (crooked, then straight).
A standard gold bar weighs about 27 pounds, and the amount of gold loaded into the ice cream truck would have overloaded the truck. It would have also caused problems from shifting during the high speed pursuit.
When Dr. Claw activates his electromagnet, one man's braces get pulled out of his mouth. In reality, tooth braces are made out of aluminum and would not get attracted to a magnet.
When Claw releases the laughing gas, some people start laughing before the gas even reaches them.
When Penny is launched from the truck in the bomb cart, nothing is visible in the truck.
When Penny is launched from the truck in the bomb cart, she is obviously laughing during the shot, even though she is supposed to be screaming and crying.
It is obvious that claw's claw is made of plastic, not metal. (When he squashes the remote with it, you can see fingerprint marks on it.
When Claw's rocket is high up in the air and it shows the overhead view of the truck and the bridge, the bubblegum is on the wrong side of the truck and the Gadgetmobile is not there.
When Claw's hearse-limo pulls up to the bluff overlooking Riverton Harbor, we see the driver reach across the dashboard and switch off the ignition key, but the sound of the car's engine had already stopped a second or two earlier.
A few times throughout the film, when claw 'snaps' his claw, the snapping noise is out of sync revealing that it is sound effects.
When Gadget is moving through the storage building where G2 is in her deactivation case, at one point a crew-member is visible for a few seconds walking around quietly in the background.
Around 2 min after the Gadgetmobile activates its rocket, the next shot shows the camera's reflection on the Gadgetmobile's passenger door.
As Dr. Claw's henchmen load their stolen laser into their car, the cameraman is momentarily reflected on the metal hoops.
Gadget uses one of G2's chips to mend his Helicopter Hat glitch; it works and he flies off the ground, yet the shot of G2 shows the camera crane's shadow - not Gadget's shadow.
One of Dr. Claw's goons gets thrown by G2 into a pile of boxes; the camera's shadow can be vaguely seen on them.
When Dr. Claw uses his weapon, time freezes all over the city of Riverton, showing several actions stopping in mid-motion and remaining in position. This means that the electronic devices in the building of the federal reserve - the gate, retina scan and the vault door - should be inoperable and impossible to function.
Claw and his minions break into the Federal Reserve and they have not even started loading the truck. the next shot shows Gadget and G2 racing towards the bank. but before they arrive, Claw and his minions seem to be stuffing around with the gold and not putting it in the truck. But there the truck is clearly fully loaded with gold when Gadget & G2 arrive. How did they get all the gold in the truck in that little amount of time?