Spike (Experiment 319) is a large dark blue porcupine-like experiment, with huge white-tipped spines on his tail, back, front legs and head, a red nose, large black eyes, black claws and a long tail that he can throw like darts. He is designed to increase a person's silliness by 99% by pricking them with his spines, leaving that person 1% clever. When Lilo discovers Mertle cheating in a contest by getting the answers from Teresa, she uses Spike on Teresa to have her give Mertle completely silly answers. His one true place is hugging--and thus taming--truant experiments at Pleakley's E.A.R.W.A.X. group, after he is given protective armor to cover his silliness-inducing spines.