It is the quintessential Carry On moment, featured in A Perfect Carry On, the documentary which forms the centrepiece of Channel 4's weekend celebrating the 40th anniversary of the first Carry On film.
But just why have these films endured? Perhaps their longevity is explained by the fact that they have more innuendo in one scene than Julian Clary could manage in a lifetime.
The author Malcolm Bradbury reckons that "the basic gags have to do with bottoms, bosoms, bodily functions of every kind, going to the lavatory or failing to do so - which is a very important theme ... The idea of humour as a broad expression of English vulgarity is actually very famous. In the 18th century, people were amazed at the sort of things the English laughed at. We do have a quite different tradition of elegant wit, but that's not here, is it?"
Clive Tulloh, executive producer of A Perfect Carry On, agrees that we have a long-standing love affair with the double entendre. "There's something peculiarly British about it. You only have to look at our choice of presenters - Larry Grayson, Julian Clary, Dale Winton. Are You Being Served? has recently been a ratings phenomenon. Controllers spend their lives trying to think up millennial programmes and we end up watching a woman ask, `Has anyone see my pussy?' We have this great seaside postcard tradition. We can't get enough of it."
Indeed. The continuing popularity of Carry On may also be a reaction against the stifling conformity of political correctness. We relish the freedom to laugh out loud at a scene in which Barbara Windsor approaches a man eating a pear and says to him: "Ooo, what a lovely-looking pear" - only to receive the inevitable Carry On response: "You took the words right out of my mouth."
According to Janet Street-Porter, a card-carrying Carry On fan, "We're surrounded by magazines and newspapers all being right-on and talking about men doing the housework and the sad role of the man at the end of the 20th century. Then you look at a Carry On film and it's a fantastic relief because it's totally politically incorrect."
Rory Sheehan, the producer/director of A Perfect Carry On, chimes in: "Kids nowadays are sick to death of being preached at. They just want to enjoy the outrageousness of a Carry On - people crashing downstairs on trolleys and bras flying off all over the place. You can imagine the two lads from Men Behaving Badly roaring with laughter - that's the target audience."
Another reason the films appeal is because viewers know what they are going to get - most of the scripts are interchangeable. "The films repeat the same old jokes - but that's what people like," Sheehan goes on. "It's the comedy of comfort and recognition. You're laughing before the joke even starts because you know exactly what's coming next. When you hear a character goes by the name of the Khazi of Kalibar, you know there are going to be 101 jokes about the Khazi."
The predictability only adds to the timeless air of the films. "What you get in a Carry On film is slapstick, panto, broad humour, and hopeless innuendo - things that transcend age, gender and country," says Street- Porter. "In a world where we do feel under stress, this kind of innocent humour will always be popular. People will always want to watch a Carry On film, just to switch off and have a laugh."
Those far-from-demanding qualities have, however, failed to endear the films to many critics - a fact which rankles with their followers. "It makes me so cross when people witter on about Powell and Pressburger or Kubrick and all these other great directors," Street-Porter continues. "But actually, with Hammer films and Carry On films, you have the two strongest categories of British films since the War. But, of course, ordinary, common people like them, and you can't call them art films. But to me they're popular art." So there.
But could the Carry On films ever come back in these days when PC rules the waves? Dale Winton, another fully-paid-up Carry On-ophile, believes you could make a Carry On now if the subject was right. He suggests a film about the Millennium Dome. And the title? Carry On Up The Erection.
A Perfect Carry On is on tomorrow at 9pm on C4 .