The Pizza Castle is a pizza place only mentioned in The Bully. It is unknown what it looks like. When SpongeBob answered Patrick's order call, Patrick thought that SpongeBob was working there now. The only known employee at this restaurant is named Mario The only known people who order there are Flats and Patrick.
SpongeBob: Death row, next in line speaking.
Patrick: (on phone) Hi, I'd like to place an order for delivery.
Patrick: (on phone) You're working at Pizza Castle now?