Deliberate mistake: When Schultz drives off with the motorcycle leaving the sidecar behind, you can see that the sidecar has been propped up. It has to be, or it would fall over. Sidecars, bringing only one wheel to the party themselves, can't stand up on their own.
Other mistake: As the camera looks at the now-crashed car, the position and condition it is in is impossible. Though funny, there is no way the car could have jumped up on the porch as shown. The front would have been crushed in, the wood of the porch damaged. The interiors of the doors are impossible given that the car would have been kept in an immaculate condition.
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