Fluff the Farting Fish by Michael Rosen
Elvie is desperate for a puppy that she can train up to do amazing tricks. But it's not a puppy Mum returns from the pet shop with, it's a fish. But Elvie doesn't give up. Determined to fulfill her dream of having a performing pet she trains up Fluff the fish. Fluff can't sit, she won't bark on command, but she does have a very special fishy talent all of her own . . .