The Playhouse Room is a secret room for your pet's house that is unlocked by building the collaborative object the Playhouse. This room was added to the game on July 5, 2010. It is only one of two secret rooms that does not cost Playfish Cash.
Like all secret rooms, you can only have one room of this type; building multiple Playhouses will not get you additional rooms. Selling the Playhouse will cause you to lose your room, so do not sell / recycle it or you will need to build a new one in order to get your room back.
Also like other secret rooms, you cannot apply wallpaper or floors to this room. However, you can decorate it with other items. This room is smaller than the regular rooms in your house.
This room will be hidden from visiting friends as long as the Playhouse object is in your inventory. Placing the object in a room in your house will allow friends to see the room.