"Cough Syrup" joke
John was a clerk in a small chemist shop but he was not much of a salesman. He could never find the item the customer wanted. Peter, the owner, had had about enough and warned John that the next sale he missed would be his last.
Just then a man came in coughing and he asked John for their best cough syrup. Try as he might, John could not find the cough syrup. Remembering Peter's warning he sold the man a box of laxative pills and told him to take them all at once. The customer did as John said and then walked outside and leaned against a lamp post.
Peter had seen the whole thing and came over to ask John what had happened.
"He wanted something for his cough but I couldn't find the cough syrup. So I substituted laxatives and told him to take them all at once," John said.
"Laxatives won't cure a cough," Peter shouted angrily.
"Sure they will," John said, pointing at the man leaning on the lamp post. "Look at him! He's too afraid to cough..."