The script allowed the prisoners to swear without offending viewers by using the word "naff" in place of ruder words ("Naff off!", "Darn your own naffing socks", "Doing next to naff all"), thereby popularizing a word that had been recorded at least as early as 1966. Ronnie Barker did not claim to have invented it. In a television interview in 2003 it was explained to him on camera what the word meant, as he said he hadn't a clue. The word was actually a piece of slang for heterosexual men which was popular among homosexual men. It was an acronym for "Not Available For F******".
The same prison infirmary set was used for the Blackadder goes Forth episode 'General Hospital'.
All who knew Richard Beckinsale were shocked and devastated by his death, particularly Ronnie Barker. He was so upset, he couldn't work for several days.
The judge reading sentencing during the opening titles is voiced by Ronnie Barker. Barker is reported to have said that he regretted recording himself as the judge (who was later portrayed by Maurice Denham in two episodes).
Porridge began life as part of a one-off series called Seven Of One for the BBC. The series featured seven separate 30 minute comedies, all starring Ronnie Barker, including an episode entitled Prisoner and Escort by Dick Clement and Ian La Frenais about the transfer of a prisoner, on New Year's Eve, from a London prison to the remote Slade prison in Cumberland and co starred Fulton Mackay and Brian Wilde, with the intention of finding potential sitcoms for Ronnie Barker to star in. Clement and La Frenais also wrote another pilot episode called "I'll Fly You For a Quid". The BBC liked both ideas and asked the writers to choose which one they wanted to develop to a full series and they chose what became Porridge. The other 'Seven of One' pilot that was chosen to go to a full series was Roy Clarke's Open All Hours which followed in 1976.