1976 commercial for TOPIC chocolate bar

Topic is a chocolate bar made by Mars, Incorporated in France and sold throughout Europe and the United States. It contains hazelnuts, nougat and caramel.

The fictional character Arnold Rimmer from the British TV sci-fi comedy Red Dwarf mentioned that he was the only person ever to buy a Topic bar with no hazelnuts in it at all. This was a joke based on the bar’s 1980s advertising slogan which claimed there was “a hazelnut in every bite”. In another episode, when Rimmer is trying to chat with Lister to distract him from thinking about food, he states that he “can’t think of another topic” – prompting the response “don’t talk about Topics, they’re food!”

The chocolate bar was promoted in a series of radio advertisements broadcast in 2002 with the strapline “A joy to eat, but a hard thing to make”.  These adverts featured actors Simon Pegg and Mark Heap who both appeared in the cult British TV comedy Spaced.

The Topic was removed from boxes of Celebrations in 2006, along with Twix. It has been speculated that the Topic was the least popular chocolate in the box, although others believe that its withdrawal was down to its similarity to the Snickers bar.

Info gleaned from Wikipedia