My Lucky Day by Keiko Kasza (2005)
When a delicious-looking piglet knocks on Mr. Fox's door "accidentally," the fox can hardly believe his good luck. It's not every day that dinner just shows up on your doorstep. It must be his lucky day! Or is it? Before Mr. Fox can say grace, the piglet has manipulated him into giving him a fabulously tasty meal, the full spa treatment (with bath and massage), and . . . freedom. In a funny trickster tale of her own, Kasza keeps readers guessing until the surprise ending when they'll realize it was piglet's lucky day all along.