Got it. Here's your riddle again:

"A son and his man are in a car accident. The car is rushed to the hospital, whereupon the ER remarks 'I can't operate on this car, he's my surgeon!' How is this possible?"

Answer: The car is a Transformer—a sentient robot who is also a surgeon. The ER recognizes the car (a Transformer) as their own surgeon.

Wild ride, but it checks out.