Eating frogs

Furkle eats one pink-kneed frog a day. Furkle doesn’t like pink-kneed frogs, but he still eats them. Somehow, he knows he must – it is very important.

How does Furkle know it is important? Was he told or did something happen to make him realise he must do it? What would happen if he didn’t eat a pink-kneed frog each day? Would his skin turn purple? Would he shrink to half his size?