Despite the title, the Wishbone family are far from happy. EMMA (Emily Watson), has a bookshop on the brink of bankruptcy, FRANK (Nick Frost) is totally overworked and exhausted, their daughter FAY (Jessica Brown Findlay) is going through those awkward teenage years as well as failing her exams and son MAX is too intelligent for his own good and consequently being bullied at school – no wonder they all fight with one another all the time! And as if this all wasn’t enough already, after being dragged to a ‘costume’ party by Emma, where they end up being the only ones in costume, the Wishbones then get cursed by an evil witch, BABA YAGA (Catherine Tate). Suddenly their ‘costumes’ become a reality – Emma is a vampire, Fay is a Mummy bandaged from head-to-toe, Max is a little, hairy werewolf and Frank, well he’s Frankenstein’s monster of course. It’s quite a shock but now the family must unite to find the witch and have her reverse the spell.
Together the newly turned monsters and their trusted family friend CHEYENNE (Celia Imrie) chase the witch half way across the world, along the way discovering that not all their new characteristics are a curse. Emma is indestructible and immortal, Frank is stronger than any superhero, Fay can hypnotise people and anxious Max is now the one inciting fear in his bullies. Their new skills are naturally very tempting at times and along the way each Wishbone wonders if it would be nice to stay a monster?