Some friends of mine volunteered for this service and the ensuing events would have made a great comedy. The people who were supposed to deliver the dog to them with all the appropriate papers didn't show up until the very last second before the plane departed, and simply handed off the dog in its pet carrier and left. My friends boarded the plane with the dog and it wasn't long before they smelled something awful; the pooch had diarrhea. The stewardess told them they needed to take the dog and the cage to the bathroom and clean it, because the other passengers were starting to gag. Obliging the stewardess, one of them took the pooch and container back to the lavatory where he cleaned it in the sink as best he could. As he was trying to get the wet, squirming pooch back into the pet carrier, it crapped all over him and the restroom. More cleanup ensued, and while he was washing the dog's belly, he saw it had a large incision with brand-new stiches. When he told my other friend of this new finding, she freaked, figuring they were now acting as mules carrying a drug-stuffed pup for someone they had never met before and began to panic about the interrogation they were about to receive in US customs on arrival. To make matters worse, the diarrhea came back with a vengeance and soon their nearby seatmates began to hurl.
Once they landed, they went to the customs agent with trembling knees, expecting the worst and wondering if they could convince the agent they were just dupes. But they lucked out; the dog was so covered in filth that the inspector didn't want to touch it, so he never saw the incision. Relieved, they passed off the pooch to the person waiting for it and then went home for a shower.