Copied from a UK site. Changed pounds for dollars
A woman brought a very limp duck in to a veterinary surgeon. As she lay her pet on the table, the vet pulled out his stethoscope and listened to the bird's chest.
After a moment or two, the vet shook his head sadly and said, "I'm so sorry, your duck has passed away."
The distressed owner wailed, "Are you sure?" "Yes, I am sure. The duck is dead," he replied. "How can you be so sure," she protested. "I mean, you haven't done any testing on him or anything. He might just be in a coma or something."
The vet rolled his eyes, turned around and left the room, and returned a few moments later with a black Labrador retriever. As the duck's owner looked on in amazement, the dog stood on his hind legs, put his front paws on the examination table, and sniffed the duck from top to bottom. He then looked at the vet with sad eyes and shook his head.
The vet patted the dog and took it out, and returned a few moments later with a cat. The cat jumped up on the table and also sniffed delicately at the bird from head to foot. The cat sat back on its haunches, shook its head, meowed softly, and strolled out of the room.
The vet looked at the woman and said, "I'm sorry, but as I said, this is most definitely, 100% certifiably, a dead duck."
Then the vet turned to his computer terminal, hit a few keys and produced a bill, which he handed to the woman. The duck's owner, still in shock, took the bill. "$150?" she cried, "$150 just to tell me my duck is dead?!"
The vet shrugged. "I'm sorry. If you'd taken my word for it, the bill would have been $20, but with the lab report and the cat scan, it's now $150."