– What, at the same time?
– Yup. This patient should have read the instructions with the utmost care.
– Professor, but isn’t acetylsalicylic acid one of the safest drugs in the market?
– It is… if you use it carefully. Misusing drugs usually leads to horrible cross-effects and, in unfortunate cases like this, to death.
Doctor Robert, how sure are we that the side effects were really caused by taking aspirin and not something else?
– The autopsy revealed that the only thing he ate before his demise was a cheese sandwich. This, and the drug, were the ultimate cause of his death. Now, on to observation room six—
– Doctor, how is it possible that a simple cheese sandwich could have these effects?
– Jesus Christ, have you read your Katzung? You there, what’s the problem?
– Uh, yes Doctor. Its just that—well—it seems odd that something as simple as aspirin could lead to such horrible results.
– Again, it wasn’t the aspirin by itself. As I’ve told you numerous times, the patient had eaten food that specifically should not be consumed before taking aspirin.
– But, a simple cheese sandwich—
– It wasn’t a ‘simple cheese sandwich’. It was alligator-cheese sandwich. Look up its fat content, it’s enough to make you grow pimples all over your body. These will spontaneously explode.
– But the constipation
– Ah yes. I suppose your book doesn’t cover that. This particular alligator was called Cynthia. Moving on…
– What about the patient’s arms? How can you lose—
– Unfortunate combination of place and time of herb picking. The sandwich contained lettuce grown in Cobija, Bolivia. That in and of itself isn’t that bad, but this one was picked on Memorial Day.
– And the burns?
– Those were actually external flames created by the patient. Comes from the rye bread having a prime number of caraway seeds per slice. The bread industry has been careless in that sense—
– And the priapism?
– A pickle. Specifically cut to be in the shape of Muncie, Indiana.

The students took notes. «Get used to it, boys»—Doctor Robert thought—«This is the first of many horrific cases you’ll see if you become doctors.»

– Any other question?

The room stood silent.

– This here is, sadly, a common case and your duty is to properly educate your patients about these dangers.
– C…common? How… how common?
– At this hospital, it’s known as “a number 8”. Now, on to observation room six.

A ReQuested writeup: «someone fill Side effects include explosive acne, terminal constipation, loss of extremities, uncontrollable pyrokinesis, and erections lasting more than four hours due to rigor mortis.»

Based on an episode of Orson's Farm called Orson's Diner. See this TVTropes entry for the exact joke.