One Rabbi says that Jewish law forbids the ingestion of Viagra on Shabbat, lest one violate the infraction of erecting a structure on the Sabbath.
But another Rabbi says that as a medication that adds pleasure to the Sabbath, it is permissible. But it is banned during Passover along with all other agents causing things to rise.
Translator
These jokes are of an unknown origin. Feel free to submit corrections or add to the list. I will edit when possible, to improve the flow and correct errors.