Revealing mistake: After the Terminator has jumped on to the truck and shot the T-1000 full of bullets he pulls the wheel to the right so that the tanker truck skids and falls but if you look closely you can see that the stunt double for the T-101 merely fakes he's pulling the wheel, and then holds onto the cab and you can see the stuntman for the T-1000 inside the cab turning the wheel before it flicks to the wider shot. (01:48:10)
Revealing mistake: When the T-800 is being attacked by the SWAT team in the Cyberdyne building, notice that in most of the shots (i.e. when he is being shot in the face, and also when the camera is behind him) Arnie has been replaced by a dummy (his skin is unnaturally pale). When the T-800 pulls out his gun and starts shooting the SWAT team, it's now back to the real Arnie, and notice how none of their bullets are now hitting his face and body, even though shots are still being fired. (02:00:20)
Revealing mistake: When the T-1000 is chasing John in the transport truck cab, the sparks always appear before the truck actually hits the walls. (02:01:20)
Revealing mistake: When the tanker truck (liquid nitrogen) is sliding along the ground the sparks can be seen not to be coming from directly under the tanker but ejecting from small canisters slightly higher up the vehicle. (02:02:55)
Revealing mistake: When the T-1000 is firing out of the hole in the windshield of the chopper, a close up shot shows that there is clear tape around parts of the window keeping all the little bits of glass together. (02:03:15)
Revealing mistake: When the Terminator's arm is caught in the wheel and he rips his own arm off and stands up, if you look closely (slow motion can help, but isn't essential) you can see his real arm stretched behind his back under his leather jacket. (02:09:30)
Revealing mistake: When the two Terminators first fight in the steel mill, in close - up shots the T-1000 is played by Robert Patrick, but in medium shots it's a stunt double who looks nothing like Robert Patrick. (02:13:55)
Revealing mistake: When the T-800 and T-1000 first begin to fight in the steel mill, the T-800 puts his fist through the T-1000's head causing him to revert to liquid metal form, then as the T-1000 is throwing the T-800 from side to side you can obviously tell that the T-1000 is just an actor wearing a highly metallic mylar suit in some shots. (02:14:10)
Revealing mistake: After the T-1000 finishes battering the Terminator with the beam, the Terminator drops to the floor and starts dragging himself. When you see the stump of his left arm move forward then backwards, the string moving the stump is visible. (02:18:15)
Revealing mistake: In the scene where John is helping Arnie up after the T-1000 has been exploded and sent to his doom in the fiery pit of molten steel (Arnie is saying "I need a vacation"), you can see how the effects crew haphazardly put on a fake busted mechanical arm underneath Arnie's coat and how it bulges out from his shoulder. You can almost see how they just tied Arnie's arm back behind his back and put a fake arm over him. (02:23:35)
Revealing mistake: Right after the T-1000 has been terminated and the T-800 is "saying goodbye" you can see the face make-up where you can see his metal endoskeleton bending with facial movement as he speaks. (02:25:00)
Revealing mistake: Before the Terminator is lowered into the steel, he says "goodbye." You can see his breath revealing the actual temperature on the set.
Revealing mistake: When the truck chase scene ends with a wheel moving in flames, Terminator and John leave on the bike leaving skid marks on the road. Watch the left side and you'll notice another skid mark from a previous take.
Revealing mistake: At the guard hut, when the Terminator goes to smash through the window you can see the different colored area and the line where the glass breaks.
Revealing mistake: During the chase on the bridge, when the Terminator opens the door of the moving car to shoot at the truck behind, it is obviously stuntman Peter Kent and not Arnie.
Revealing mistake: When the Terminator stabs the guy leaning over the pool table, on the last shot of him, aching, check a protruding hump on his back, revealing where a safety pad was placed under his clothes.
Revealing mistake: When the T-800 is reloading his shotgun in the alley with John, he reaches into his pocket, presumably to grab shells for the shotgun. In the shot with him and John in frame, his hand comes out of his pocket empty, but we hear him load another shell into the gun in the next shot.
Revealing mistake: When the T-1000 goes to kill the guard in the mental hospital, from the angle looking at the T-1000 the seam where the prosthetic matches into the guard's skin is visible.
Revealing mistake: In the scene where the Terminator has just broken Sarah out of the hospital and the T-1000 has been shot off the back of the cop car you can see his "metal" arms bending as he rolls across the pavement, and as he gets back to his feet you can see where his real hands are.
Revealing mistake: When the cop by the vending machine is about to be killed by the T-1000, the back shot of him reveals he's been replaced by an obvious mannequin. His perfectly trimmed hair along the nape is now long and messy, and a long stitch appears along his sideburn and down to the neck.
