The Sponge and Cheese Costumes are from the Clam's mission and the February 2006/April 2017 Account Upgrades. Sponge pets are made of soft, porous material and have bunches of holes, borders, and soapy bubbles. (For more info, these pets draw inspiration from the tool, not the animal.) Cheese pets are Swiss-based, being full of holes (also known as "eyes"), based on the cliché of most blocks of cheese resembling Swiss cheese in classic cartoons.