Some cast members that played prisoners have noted that throughout the series if you showed up late to the set your punishment would be that your character would either die or be raped the next week.
This was the first one-hour drama ever produced by HBO.
The arm that is being tattooed in the opening credits belongs to series creator Tom Fontana. The tattoo artist kept retracing his needle work so the crew could get the best take. Eventually the artist stopped saying that he "can't let this guy bleed anymore."
The two inmates who were brothers, Ryan and Cyril O'Reilly, were played by real-life brothers Dean Winters and Scott William Winters, respectively. Their other brother Bradford Winters was one of the writers for the show.