Revealing mistake: When Shooter pins Mort against the tree with the shovel, you can see that it's a rubber shovel because it's bending around Mort's neck. [Mentioned on commentary]. (00:40:45)
Revealing mistake: When Mort stops at the gas station to talk to Ted, and he gets out of his Jeep, the key is still in the ignition but there's no dinging from the door being opened (which we know it does from an earlier scene).