The lady teacher asks the pupils what kind of medicines they know of,
and what they are used for:
The first pupil said: Panadol?
Very good! And what is it used for?
It is used for headache.

The second pupil said: Piriton.
Excellent. And what it is used for?
To help you sleep.
Now it is Johnny's turn and he said: Viagra
So, Johnny, what is it used for?
I think it can be used to stop diarrhoea.
Who told you this?
Nobody, but every evening my mother tells my father...
“Take a Viagra, maybe that little shit will get harder.”
The teacher had to leave the room!