At the time this did the rounds (it was big at the start of last year when it really got picked up by blogs which circulated it withough any background) I did dig out all the relevant info including an interview with Jeffrey but the
Wikipedia entry will do:
The "Adult" version
In 1978 the cast and crew of Rainbow made a special edition of Rainbow for ITV staff. This show featured plenty of sexual innuendo and although not shown at the time, it has since been aired for the amusement of those who grew up with the show. (It should be noted that the external page linked below erronously claims that the episode was publically broadcast).
I read somewhere that it was made as a birthday present for one of the producers of Rainbow. It later surfaced on Australian TV as an example of how British children's TV is full of inuendo (which it isn't).
As someone said, it's been on channel 4 a few times now...
Is this the twangers thing? It was first shown on the Victor Lewis Smith show, TV Offal, in the nineties.
There's also an adult version on a Jim Davidson programme which Smith showed a clip of where Zippy talks about "the fucking Garden of Eden". I remember the Rainbow gang turning up as a gag on a Davidson show in the eighties, except with no swearing (but plenty of innuendo).
Don't ask me what I was doing watching Jim Davidson.
Geoffrey Hayes from Rainbow had this to say about it:
"The VT department of each ITV company, every Christmas had a competition to enter all the outtakes from their particular companies programme output, and see which ones were the funniest. But ours wasn't an outtake, we specially did it. It was specially scripted and we did it and I never saw it! We did it and Thames won it, but what they actually won, I don't know. But I never saw the video. I can't remember much about it except for Zippy with a banana. The script was written by the voice of Zippy and George; Roy Skelton."