In at least two episodes ("Lost Spell" and "The War of the Sexes"), it's Maurizio, not Jacob, who figures out the way to break the spell. Both times it had to do with one of The Four Loves - his friendship with Jacob, and Mr. Cosy's paternal instinct, respectively.
By episode
"The Beastie Brew": Why is it that even after Jacob and Maurizio gathered all the people-turned-animals from the city on the ship, the list was still incomplete? Because the lawyers-turned-sharks were in the water, not on land. And it wasn't until the ship started to sink that the sharks could technically get on board, thus completing the list and breaking the spell.
"The War Of The Sexes": It's actually possible (though admittedly not easy) to solve the riddle before the heroes. Throughout the show, Tyrannia would sometimes call herself Jacob's "mommy", and in this episode, despite them being of the opposite sexes, shows no hostility towards him, instead telling him to stay where it's safe. Now, what breaks the spell? Mr. Cozy going Papa Wolf on the seemingly feral Maurizio to protect his daughter. The familial kind of love has been the answer all along!
