You shouldn't eat food that isn't yours.
Joey's date Melinda is in the restaurant restroom when their desserts arrive, and after taking a bite of his own, Joey realizes that he hates it.
Joey wants to enjoy some dessert.
Joey flags down the waiter and asks for the same dessert that Melinda ordered.
Joey eats some of Melinda's dessert while she is in the restroom.
Melinda offers Joey some of her dessert while he waits for his own.
Melinda is upset when she returns and decides to end the date early.