Nicknamed Fatso, Murdo's mum decides he'll have to lose weight. She wants to buy him a dog to walk for exercise, but Murdo prefers Rosie, the rat he sees in the pet shop, and begs to keep her. The walks don't quite work out, but Murdo gets plenty of exercise looking for Rosie when she disappears.
Used availability for Alison Prince's Fatso's Rat
October 1997 : UK Paperback