Although the snack is largely aimed at children, it is enjoyed widely by people of all ages.
Monster Munch was launched in Britain in 1977 by Smiths. Originally called “The Prime Monster” (a play on “The Prime Minister”, and as part of a wider campaign), the decision was taken to rename the snack “Monster Munch” in 1978. Advertised as “The Biggest Snack Pennies Can Buy” – in reference to the large size of the crisps – each pack featured a different monster on the front of the packet. There was even a “Monster Munch Club” available, whose members received a “Monster Munch Munchers” membership pack which included a membership card, pen, several story books, and a story tape which included six “tall stories” and accompanying songs.
Info gleaned from Wikipedia