Josh and Danny let Petty Potts-their barmy next-door neighbour and scientist extraordinaire-give them a lift to school, but after a mix up with their drink and some S.W.I.T.C.H spray the twins suddenly have green feelers, ears in their abdomens and a strange ability to chuck up brown goo.

The boys must SWITCH back before anyone notices they're not in class.

But school is the least of their worries-they're just a whisker away from trouble-there's a grasshopper muncher on the loose . . . Petty Potts's diary entry:One day, I am going to find Victor Crouch-confront him-and make him confess that he stole my work and burnt out my memory. But in the meantime, as far as Josh and Danny are concerned, I will keep my promise and will never make them try any more spray or potion. Or trick them. Or bribe them. Or anything like that. Probably.