The Gro Company - Gro-Egg Shell (Cover) - Mikey the Monkey. Percy the Penguin is one of three collectable characters that are fun companions to the Gro-egg. The Gro-egg Shells maintain all of the Gro-egg's current features including its important night light and temperature reading functions. Percy the Penguin makes the Gro-egg more decorative and visually appealing for both children and adults, while maintaining its practical safety features that so many parents have come to rely upon to ensure their children have a safer night's sleep. A fun accessory that sits on top of your Gro-egg. Adds personality to your practical Gro-egg. To be used with the Gro-egg digital room thermometer. Surface clean only.