In 1979, the cast and crew of Rainbow made a special exclusive sketch for the Thames TV staff Christmas tape, sometimes referred to as the "Twangers" episode. This show featured plenty of deliberate sexual innuendo (beginning with Zippy peeling a banana, saying "One skin, two skin, three skin, four..." before being interrupted), and never shown at the time (as it was never intended to be screened to the general public.) It also included Geoffrey convincing the viewers to play with their balls, but if they didn't have any balls, they could ask a friend and play with his. Jane also claimed that she was banging with Rod and Roger. Soon, Zippy asked them to stop suggesting whether to play with a blowing tube and maraccas, so they could start singing the 'Plucking Song'.
The clip became famous after being aired on Victor Lewis-Smith's Channel 4 programme TV Offal (1997) and was jokingly referred to as "the pilot episode", which it clearly wasn't as Geoffrey Hayes was a presenter at the time. The clip has become widely-spread, first in emails as an attachment and later via online video websites such as YouTube. This has led to many erroneous claims that the episode was publicly broadcast as a regular episode.