Mr. Smith goes to the doctor's office to collect his wife's lab test results.

The lab technician says: "I'm sorry, sir, but there has been a bit of a mix-up and we have a problem. When we sent the samples from your wife to the lab, the samples from another Mrs. Smith were sent as well and we are now uncertain which one is your wife's. Frankly, it's all either very bad or terrible!"

"What do you mean?" said Mr. Smith.

"Well, one Mrs. Smith has tested positive for Alzheimer's, and the other Mrs Smith has tested positive for AIDS. We can't tell which is which."

"That's terrible! said Mr. Smith. Can we do the test over?"

"Normally, yes. But you have Ontario Health Care, and they won't pay for these expensive tests more than once."

"Well, what am I supposed to do now?" said Mr. Smith.

"Ontario Health Care recommends that you drop your wife off in the middle of town. If she finds her way home, don't sleep with her." :)