From the bestselling creator of Grumpycorn! Unicorn, Narwhal, Mermaid and Jellyfish are ready for an adventure, and, as Unicorn quite rightly points out, nothing is more adventurous than travelling into SPACE. But when the four friends disagree over which planet to visit first, Unicorn most definitely turns into a very grumpy Grumpycorn and decides to go off on his own. Will Unicorn see the error of his ways? Will he realise that friendship is what makes everything fun?

Will he finally stop being such a Grumpycorn? There's only one way to find out...