Humour used well in advertising is gold and this Selleys offering is a great example of humour being used well. It is also a great example of using fear as a motivator. The idea of using fear may sound a little, well, immoral. But it's not as bad as it sounds. There are two ways to motivate someone to do something (like make a purchase). People are motivated to act because they believe they will either gain pleasure of avoid pain. Of those two, fear is a the stronger motivator. Most advertising we experience works hard to create desire. That motivates people by creating the perception they will gain pleasure. The best way to make the fear concept more palatable is to water it down with humour and it works well here. Humour is one of the crucial components that can make something go viral. You've gotta love the double entendre - they could be suggesting that someone will do your job, but we know they are suggesting someone will do your wife. The product chosen (gap filler) could not have been a coincidence!