The Princess in Black and the Bathtime Battle by Shannon Hale

Everyone’s favourite princess returns for her smelliest battle yet. A foul cloud is plaguing the goat pasture, but every time the Princess in Black and her friend the Goat Avenger manage to get rid of the odour, they accidentally blow it to another kingdom! Other masked heroes and their trusty companions show up to help, but how do you battle a stench when your ninja moves fail? Featuring three new princess superheroes and an unbearably big stink.