The Not-So Scary Snorklum

Over the hill stomped a huge, hungry Snorklum. 'I am the scary Snorklum!' he roared, 'and I am going to have Mole sandwich for tea, with a little salt and pepper and chunky pickle.' But the Snorklum is scared of something too! Why do his knees knock, his tail twitch, and his whiskers wibble in a worried sort of way?