Factual error: The electric guitar Marty plays at the "Enchantment Under the Sea Dance" is a Gibson ES345. This guitar model debuted between 1957 and 1958 yet he's supposedly playing it in 1955. It would have been more accurate to have him using a Fender Telecaster (1950) or Stratocaster (1954) or a Gibson Les Paul (1952). (01:23:50)
Factual error: While the problem with refuelling the SR71 is a real one for D.A.R.Y.L., he is never going to get that far. The SR71 had no self starters and required a trained crew with a starter generator mounted on a truck to get the engines going in the first place. D.A.R.Y.L. just pushes a button and away he goes. Not likely.
Factual error: Two of the huge rocks which plummet from the roof of the cave hit the water and then bob to the surface again. Pumice is the only rock which floats on water, but this rock is white and pumice is grey, and pumice is too light and porous to form cave walls anyway.
Factual error: Towards the end when Pee Wee is being chased through the sound stage, he comes out through the open doors and the red light is flashing that indicates that filming is going on. But if the light were on, the doors would not be open. They also take a while to open, so it's not like they could have just swung open right before Pee Wee got there. (01:14:30)
Factual error: The word 'magician' is spelled 'magicinan' on the cart when Nicholas bends down to collect the spiders web. (00:50:30)
Factual error: When the aliens first take over the Thunder Road, Wolfgang says that he will reverse the "x-axis diode" to make the computer think they are traveling in the opposite direction. However the outside view shows them moving up and forward at a steep angle, ie moving up on the Z axis and forward on the X axis. If they X axis diode was reversed then the Thunder Road would still be ascending at the same rate, simply in the opposite direction (basically changing from moving forwards and climbing to moving backwards and climbing) . To make them descend, he would have to reverse movement on the Z axis. Considering it's shown on screen that Wolfgang designed the interface to make the sphere move on XYZ coordinates, he would know this.