Ever since my son, Jordan, saw Debbie Brown's worm cake, he has obssessed about having it as his 6th birthday cake. This is my version, on cupcakes (ran out of time to make him a bigger cake).
He was really excited when he saw his worm cupcakes and kept running up to me to tell me how much he loved his 'wigg-e-ly worms'. This is the part I find most satisfying with children's birthday cakes - they fall in love with their cakes and bubble over with excitement.
The worms would look really cute too as caterpillars. Perhaps for a 'very hungry caterpillar' party?