Shape Shifters

Lei-lei is a new girl at Penny's school. Acacia the class bully tries to steal her lunch but Lei-lei has special 'shape shifting' skills and briefly uses them to change Acacia into a prickly tree and stops her bullying. Penny is intrigued and wants to learn shape shifting but shape shifting can be dangerous if used for the wrong reasons, will it be ok or will Penny find it too hot to handle?