On the Continent, this unremarkable cleaning product is known simply as Cillit. The 'Bang' is a triumph of British ingenuity. In JWT's no-nonsense slogan, it suggests instant effect - something hammered home in the product's commercials, in which a dirty coin turns shiny before your very eyes (a caption admits that the party trick actually takes 15 seconds.)
We can blame the TV advertising, not the slogan, for Cillit Bang's fame: with its shouting front-man ('Hi! Barry Scott here!') and retro look, it appeals to young viewers because 'it's so bad that it's good'. Legend has it that the first commercials were made by JWT's Budapest office and repurposed for the UK market - but it quickly became a successful strategy for the internet generation.
Not only are there numerous disco 'remixes' of the ad online, the fictional 'Barry Scott' has his own weblog. But a little of this stuff goes a long way. Maker Reckitt Benckiser has now switched agencies. Bang - and the account was gone!