In the burglar skit, Bam has nothing on his head when him and Johnny first land on the ground. In the next shot, he has a black cap on.
In the opening scene, where Johnny Knoxville is taking the rental car to the shop, in the top left corner, a boom mic is clearly visible. This is a reality film that breaks the fourth wall constantly - crew/equipment visible goofs are not mistakes in this genre.
In the X-Ray scene when Ryan Dunn first meets the doctor you can clearly see that there is already an X-ray shot with a toy car in rectum hanging behind doctor's back. That was from another appointment that the crew didn't get the desired reaction from.
The rental car employees fail to notice that the car has been in a demolition derby, with having spray painted numbers and a few modifications to the interior, despite Johnny Knoxville saying that the car had been involved in a wreck.