Book 6 in the laugh-out-loud invention series - a must-have for fans of Wimpy Kid and Captain Underpants. Dannny Dingle, Super Genius Inventor, has returned, and this time - it's serious! After an awful parents' evening, Danny and Percy's friendship is on the rocks. Thanks to Mr Hammond spilling the beans about their couscous-projecting particle accelerator, they've been grounded until they're twenty-one! And what's more, they've got to compete against each other in the school's first ever parent-child sports day.