It is a litter box located in a private room in SpongeBob's house that serves as a bathroom for Gary and contains a sliding pet door. The box is orange in color and depicts Gary's name written in yellow on one side. It is filled with litter for Gary to urinate or defecate on.
Role in series
SpongeBob convinces Gary to abandon Patrick and return to him. During the process, the former dumps the litter in the box onto himself and tells Gary that he doesn't need to use his litter box for bathroom purposes anymore and can go anywhere he likes.
SpongeBob tries looking for Gary and presumes he is in his litter box, due to the Seaweed Noodle Stew he was fed the preceding night. SpongeBob plugs his nose with a noseclip and pops his head through the sliding door to find Gary, but doesn't see him there.
SpongeBob tosses the Sizzlemaster (controled by Plankton) into Gary's litter box which the Sizzlemaster has to clean and SpongeBob walks off. Plankton barks at Karen for adding "smell sensors" to the Sizzlemaster.
Plankton hides from Gary in his litter box. He munches on the snail litter and says that it tastes better than pineapple which he hates very much. He swallows the litter and continues searching through SpongeBob's house to find the Krabby Patty secret formula.