The Fisher-Price Hedgehog Shaker Twins are oh-so-fun for your baby's little hands to shake, rattle, and roll around. Each of these adorable shakers has smooth "quills" and rattle beads inside for exciting shake-em-up play! Where development comes into play. Sensory: Each hedgehog has a different rattle sound when shaken to engage and excite your baby's auditory senses. Gross Motor: Grasping and shaking their hedgehog pals help strengthen your baby's fine and gross motor skills.