When K.I.T.T. uses his sub-zero mode to freeze his insides, all his windows steam up except the one in the back.
The picture of Bianca that Michael finds in Harley's house changes. The first time it is shown she is looking up, the second time she's looking down. Further more, it was made in the scene where she meets Cooper at the retreat, which happened just moments before Michael found the picture and after Harley had already been killed.
When Michael is driving towards the SI-14 restaurant, the driver is wearing a black jacket, but in the next scene, Michael is clearly in a brown jacket.
When KITT is pulling Michael to get him airborne, KITT's front grille appears and disappears between shots.
When KITT engages sub-zero, his entire interior is filled with cold and fog. However, the monitor showing the interior temperature shows no traces of fog on it.
When K.I.T.T. turbo boosts over the 4x4, a finger is seen pressing the Turbo Boost button even though nobody is driving K.I.T.T. at the time.
When Bianca gets out of the hot tub in the opening scene, she wraps the towel around her and turns to her left. Just above the towel lining on her back, an undergarment is visible.
When Michael is driving towards the SI-14 restaurant, a circular steering wheel is clearly visible.
The dart that gets shot into the courier's back tire is clearly not a dart at all, but a matte-black arrow that's been drawn into the frame.
When KITT crashes through the gate of the retreat, it's clearly a toy car - the hub cabs are missing their texture and the rear spoiler is larger than usual.
(at around 24min) The film of K.I.T.T. stopping at the side of the road is played backwards. You can notice it when you pay attention to the dust. The same shot is used later at 27 min when K.I.T.T., reverses but then it is played forwards.
A cloth draped behind the driver's seat in KITT is seen when he is attempting to stop the 4x4. The driver is underneath looking though the space between the headrest and top of the seat.
When Michael dives to avoid the electric wand, and the bolt hits the tree trunk, you can clearly see the squibs taped to the tree.
When KITT opens his door to let the tiger out, the camera crew is reflected on his door.