Actually, it wasn't shown on TV. It was, apparently, a practice for TV crews to shoot "Christmas tapes" that they would then show at their Christmas parties. They were then, of course, purposely crude / raunchy, because they were meant to be shown as an inside joke for adults.
These were never shown on TV, until Channel 4 in the UK aired a show called "TV Offal" in the late 1990s.
have you ever seen any of the Rainbow books that are floating around? They're full of this sort of stuff and other amusing bits, aimed at the original audience.