Doctors advise against tattooing penis — here's why

From LiveScience:

A 21-year-old Iranian man now suffers from a permanent erection after getting a tattoo on his penis, according to a report of his case.

The man had the Persian phrase "borow be salaamat," meaning "good luck with your journeys," tattooed on his penis. He also had the letter M, the first letter of his girlfriend's first name, tattooed on it, according to the report.